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Math Topic - Speed, Distance & Time

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Published in: Mathematics
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Helpful Notes for students who are preparing for competitive exams.

PBI I / Jalandhar

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  1. PBI Important Facts and Formulae PBI INSTITUTE Speed, Distance & Time 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. Distance speed _ Time Distance Time = speed Distance = (Speed x Time) km/hr to m/sec conversion x km/ hr = (x / 18 ) m [sec. m/sec to km/hr conversion: x m/sec = (x x 18/ 5 ) km/ hr. If the ratio of the speeds of A and B is a : b, then the ratio of the times taken by then to cover the same distance is 1/ a : 1/ b orb : a. Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then,the average speed during the whole journey is (2xy / x + y )km/hr. Time taken by a train of length I metres to pass a pole or a standing man or a signal post is equal to the time taken by the train to cover I metres. Time taken by a train of length I metres to pass a stationary object of length b metres is the time taken by the train to cover (l + b) metres. Suppose two trains or two objects bodies are moving in the same direction at u m/s and v m/s, where u > v, then their relative speed is = (u - v) m/s. Downstream/Upstream In water, the direction along the stream is called downstream. The direction against the stream is called upstream. If the speed of a boat in still water is u km/hr and the speed of the stream is v km/hr, then Speed downstream = (u + v) km/hr. Speed upstream = (u - v) km/hr. If the speed downstream is a km/hr and the speed upstream is b km/hr, then Speed in still water = 1/2 (a + b) km/hr. Rate of stream = 1/2 (a - b) km/hr.
  2. PBI PBI INSTITUTE 1. Solution EXERCISE A man in a train notices that he can count 21 telephone posts in one minute. If they are known to be 50 metres apart, then at what speed is the train traveling? A. 55 km/hr C. 60 km/hr Number of gaps between 21 telephone posts — Distance travelled in 1 minute Speed of the train traveling is = 60 km/hr. B. 57 km/hr D. 63 km/hr - 20. = (50 x 20)m = 1000m = 1 km. 2. A man walking at the rate of 5 km/hr crosses a bridge in 15 minutes. The length of the bridge (in metres) is A. 600 c. 1000 Solution speed Distance covered in 15 minutes B. 750n D. 1250 = 25/18 m/sec. = (25/18 x 15 x 60)m = 1250 m. 3. A person has to cover a distance of 6 km in 45 minutes. If he covers one-half of the distance in two-thirds of the total time; to cover the remaining distance in the remaining time, his speed(in Km/hr) must be c. 12 Solution Remaining distance Remaining time Required speed D. 15 = 3 km/ hr = (1/3 x 45) min = 15 min = 1/4 = (3 x 4) km/hr = 12 km/hr. 4. A person travels from P to Q at a speed of 40 km/hr and returns by increasing his speed by 50%. What is his average speed for both the trips? A. 36 kmph C. 48 kmph Solution Speed on return triP= • 150% of 40 Average speed B. 45 kmph D. 50 kmph = 60 kmph. x 40 x 60/40+60)km/hr = (4800/100)km/hr = 48 km/hr.
  3. PBI 5. A car moves at the speed of 80 km/hr. second? A. 8 m/sec C. 21x2/9 m/sec PBI INSTITUTE what is the speed of the car in metres per B. 20x1/9 m/sec D. m/sec Solution speed 6. = (80 x 5/18) m/sec = 200/9 m/sec = 22x2/9 m/sec.s A and B walk a circulat track. They start at 8 a.m from the same point in the opposite directions. A and B walk at a speed Of 2 rounds per hour and 3 rounds per hour respectively. How many times shall they cross each other before 9.30 a.m? Solution Relative speed D. 11 = (2+3) = 5 rounds per hour. So, they cross each other 5 times in an hour and 2 times in half an hour. Hence, they cross each other 7 times before 9.30 a.m. 7. The distance between two cities A and B is 330 Km. A train starts from A at 8 a.m. and travel towards B at 60 km/hr. Another train starts from B at 9 a.m and travels towards A at 75 Km/hr. At what time do they meet? A. 10 a.m C. 11 a.m Solution Suppose they meet x hrs after 8 a.m. then (Distance moved by first in x hrs) + = 330. [Distance moved by second in (x-1) B. D. 10.30 a.m 11.30 a.m hrs] Therefore 60x+75(x-1) So,they meet at (8+3). i.e lla.m. < = > 330. 8. An aeroplane covers a certain distance at a speed of 240 kmph in 5 hours. To cover the same distance in Ix2/3 hours, it must travel at a speed of A. 300 kmph C. 600 kmph Solution Distance Required speed B. 360 kmph D. 720 kmph = 1200 km. = (1200 x 3/5)km/hr = 720 km/hr.
  4. PBI PBI INSTITUTE 9. A truck covers a distance of 550 metres in 1 minute whereas a bus covers a distance of 33 kms in 45 minutes. The ratio of their speed is Solution Ratio of speeds D. 50 : 3 x 18/5) : (33/45 x 60) = 33 : 44 10. A boy goes to his school from his house at a speed of 3 km.hr and returna at a speed of 2 km/hr. If he takes 5 hours in going and coming, the distance between his house adn school is A. 5 km C. 6 km Solution Average speed Distance traveled B. 5.5 km D. 6.5 km = (2 x 3 x 2/3+2)km/hr = 12/5 km/hr. = (12/5 x 5)km = 12 km Distance between house and school = (12/ 2)km =6 km 11. A man on tour travels first 160 km at 64 km/hr and the next 160 km at 80 km/hr. The average speed for the first 320 km of the tour is A. 35.55 km/hr B. 36 km/hr C. 71.11 km/hr D. 71 km/hr Solution Total time taken = (160/64 + 160/8)hrs = 9/2 hrs. Average speed = (320 x 2/9) km.hr = 71.11 km/hr. 12. An athlete runs 200 metres race in 24 seconds. His speed is A. 20 km/hr C. 28.5 km/hr Solution speed 13. B. 24 km/hr D. 30 km/hr = 200/24 m/sec = 25/3 m/sec = (25/3 x 18/5) km/hr = 30 km/hr. An express train travelled at an average speed of 100 km/hr, stopping for 3 minutes after every 75 km. How long did it take to reach its destination 600 km from the starting point?
  5. PBI PBI INSTITUTE A. C. Solution 6 hrs 21 min 6 hrs 27 min B. D. = (600/100)hrs =6 hrs. = 600/75 - 1 = (3 x 7)min =21 min. 6 hrs 24 min 6 hrs 30 min Time taken to cover 600 km Number of stoppages Total Time of stoppages Hence,total time taken=6 hrs 21 min. Sound is said to travel in air at about 1100 feet per second. A man hears the axe 14. striking the tree, 11/5 seconds after he sees it strike the tree. How far is the man from the wood chopper? A. 2197 ft C. 2500 ft Solution Distance B. 2420 ft D. 2629 ft = (1100 x 11/5)feet = 2420 feet. 15. The speed of a car increases by 2 kms after every one hour. If the distance travelling in the first one hour was 35 kms. what was the total distance traveled in 12 hours? A. 456 kms C. 552 kms Solution Total distance travelled in 12 hours This is an A.P with first term, a=35, number of terms, Required distance B. 482 kms D. 556 kms . ...upto 12 16. terms) = 12/2[2 x 35+{12-1) x 2] = 552 kms. A person crosses a 600 m long street in 5 minutes. What is his speed in km per hour? A. 3.6 C. 8.4 Solution speed 17. B. 7.2 D. 10 / 5 x 60)m/sec = 2 m/sec x 18/5)km/hr = 7.2 km/ hr. A train travels at an average of 50 miles per hour for 2x1/2 hours and then travels at a speed of 70 miles per hour for Ix1/2 hours. How far did the train travels in the entire 4 hours? A. 120 miles C. 200 miles B. 150 miles D. 230 miles
  6. PBI Solution Total distance travelled PBI INSTITUTE = [(50 x = (125+105)miles = 230miles. 18. Two trains 200 m and 150 m long are running on parallel rails at the rate of 40 kmph and 45 kmph respectively. In how much time will they cross each other, if they are running in the same direction ? A. 72 sec C. 192 sec Solution Relative Speed Time taken B. 132 sec D. 252 sec = (45 - 40 ) Kmph = 5 kmph =(5 x 5/ 18)m/sec = (25/ 18 ) m/sec = (350 x 18/ 25) sec = 252 sec. 19. A train 110 m long passes a man, running at 6 km/h in the direction opposite to that of the train, in 6 seconds The speed of the train is A. 54 km/hr C. 66 km/hr Solution Speed of the train relative to man speed of the train be x kmph. Relative Speed 20. A speed of 14 meters per second is the same as A. 28 km.hr C. 50.4 km/hr Solution speed B. 60 km/hr D. 72 km/hr = (110/ 6 ) m/sec km/hr = 66 km/hr + 6) kmph. = x + 6 = 66 x = 60. B. 46.6 km/hr D. 70 km/hr = 14 m/ sec 21. =(14 x 18 / 5)km/hr = 50.4 km/hr A train travelling at a speed of 75 mph enters a tunnel 3 1/2 miles long. The train is 1/4 mile long. How long does it take for the train to pass through the tunnel from the moment the front enters to the moment the rear emerges? A. 2.5 min C. 3.2 min Solution Total distance covered B. 3 min D. 3.5 min = (7/2 + 1/4) miles = 15/ 4 miles
  7. PBI IN Time taken PBI INSTITUTE = (18 x 5 /18) km/hr = (15/4 x 75) hrs = 1 /20 hrs = (1 / 20 x 60) = 3 min. 22. A 300 meter long train crosses a platform in 39 seconds while it crosses a signal pole in 18 seconds. What is the length of the platform ? A. 320 m C. 650m Solution speed Length of the platform be x metres. Then 23. B. 350m D. None of these = (300 / 18) m/sec = (50 / 3) m/sec. = x + 300 /39 = 50 / 3 m/sec = 3 (x + 300) =1950. = 350 m A train takes 18 seconds to pass completely through a station 162 m long and 15 seconds through another station 120 m long. The length of the train is A. 70m C. 90m Solution Let the length of the train be x metres. B. 80m D. 100m 24. = x + 162/ 18 -x + 120/ 15 = 180+120) 90. How many seconds will a 500 metre long train take to cross a man walking with a speed of 3 km/hr in the direction of the moving train if the speed of the train is 63 km/hr ? A. 25 c. 40 Solution Speed of train relatively to man Time taken to pass the man B. 30 D. 45 = ( 63 - 3)km/hr = 60 km / hr = (60 x 5/ 18)m/sec = (50 / 3) m/sec = (500 x 3/ 50)sec = 30 sec.
  8. PBI PBI INSTITUTE 25. Two trains, one from Howrah to Patna and the other from Patna to Howrah, start simultaneously. After they meet, the trains reach their destinations after 9 hours and 16 hours respectively The ratio of their speeds is B. D. = (A'S speed) . speed) = V 16 : V 9 9: 16 Solution Let us name the trains as A and B. 26. Two trains 100 meters and 120 meters long aer running in the same diredtion with speeds of 72 km/hr and 54 km/hr. In how much time will the first train cross the seconds? A. 40 C. 46 sec Solution Relative Speed of trains Time taken to cover B. 44 sec D. 48 sec = (72 - 54) km/hr = 18 km/hr = (18 x 5/18) km/hr = 5 m [sec. = (100 + 120) m/sec = (220/5 ) sec = 44 A train 220 m long is running with a speed of 59 kmph. In what time will it pass a man who is running at 7 kmph in the direction opposite to that in which the train is going ? A. 12 sec C. 16 sec Solution Speed of the train Time taken by it cover 220m at (55/3) m/sec B. 15 sec D. 18 sec = (59 + 7) kmph = (66 x 5 / 18) m/sec = (55 / 3) m/sec. = (220 x 3/55) sec = 12 sec. 28. A train 360 m long is running at a speed of 45 km/hr. In what time it will it pass a bridge 140 m long? A. 40 sec C. 45 sec Solution speed Total distance covered B. 42 sec D. 48 sec + 5/ 18)m/sec / 2)m/sec + 140
  9. PBI Required time PBI INSTITUTE =500 m x 2/ 25)sec = 40 29. A train covers a distance of 12 km in 10 minutes. If it takes 6 seconds to pass a telegraph post, then the length of the train is A. 90 m C. 120m Solution speed Length of the train B. 100m D. 140m = (12/ 10 x 60)km/hr = (72 x 5/18) m/sec = 20 m/sec. = (speed x time ) = (20 x = 120 m. 30. Two trains travel in opposite directions at 36 kmph and 45 kmph and a man sitting in slower train passes the faster train in 8 seconds. The length of the faster train is A. 80m C. 120m Solution Relative speed Length of the train 31. A train 132 m long A. 70 km/hr C. 79.2 km/hr Solution speed 32. A train 240 m long platform 650 m long ? A. 65 sec C. 100 sec Solution speed Required time B. 100m D. 180m = (36 + 45) km/hr = (81 x 5/18) m/sec = (45 / 2) m/sec = (45/2 x 8) m = 180 m. passes a telegraph pole in 6 seconds. Find the speed of the train B. 72 km/hr D. 80 km/hr = (132 / 6) m/sec = (22 x 18 /5)km/hr = 79.2 km/hr passed a pole in 24 seconds. How long will it take to pass a B. 89 sec D. 150 sec = (240 / 24) m/sec = 10 m/sec = (240 + 650/10) sec = 89 sec. 33. A train of length 150 metres takes 40.5 seconds to cross a tunnel of length 300 metres. What is the speed of the train in km/hr ?
  10. PBI IN B. D. PBI INSTITUTE 26.67 66.67 A. c. Solution speed 13 33 40 + 300 / 40.5)m/sec 5) km/hr = 40 km/hr 34. In what time will a train 100 metres lomg cross an electric pole, if its speed be 144 km/h r? A. 2.5 seconds C. 5 seconds Solution speed Time taken B. 4.25 seconds D. 12.5 seconds = (144 x 5/ 18)m/sec = (100 /40 ) sec = 2.5 sec 35. A train 280 m long, running with a speed of 63 km/hr will pass a tree in A. 15 sec. C. 18 sec. Solution speed Time taken B. 16 sec. D. 20 sec. = (63 x 5/18) m/sec = 35/2 msec = (280 x 2 /35)m/sec = 16 sec. 36. A train running at the speed of 60 km/hr crosses a pole in 9 seconds. What is ihe length of the train ? A. 120 metres C. 324 metres Solution speed Length of the train B. 180 metres D. None of these = (60 x 5/18) m/sec = (50 / 3) m/sec = (speed x Time ) = (50/3 x 9) m = 150 m. A jogger running at 9 kmph alongside a railway track is 240 metres ahead of the engine of a 120 metre long train running at 45 kmph in the same direction. In how much time will the train pass the jogger ? A. 3.6 sec C. 36 sec Solution Speed of train relative to jogger B. 18 sec D. 72 sec = (45 - 9) km/hr = 36 km/hr
  11. PBI IN Distance covered Time taken PBI INSTITUTE = (36 x 5/18) m/sec = 10 m/sec = (240+120) m = 360 m = (360 / 10)sec = 36 sec. 38. Two goods train each 500 m long, arc running in opposite directions on parallel tracks. Their speeds are 45 km /hr and 30 km/hr respectively Find the time taken by the slower train to pass the driver of the faster one. A. 12 sec C. 48 sec Solution Relative speed Total Distance covered Required time B. 24 sec D. 60 sec = (45 + 30 )km/hr = (75 x 5/18)m/sec / 6) m/sec = (500 + 500) m = 1000 m = (1000 x 6/125)sec = 48 39. A 270 metres long train running at the speed of 120 kmph crosses another train running in opposite direction at the speed of 80 kmph in 9 seconds. What is the Length of the other train ? A. 230 m C. 260 m Solution Relative Speed B. 240 m D. 320 m = (120 + 80)km/hr = (200 x 5/18)m/sec = (500 / 9)m/sec Let the length of the other train be x Then, x + 270 / 9 metres 40. x + 270 = 500 x = 230. A train 220 m long is running with a speed of 59 kmph. In what time will it pass a man who is running at 7 kmph in the direction opposite to that in which the train is going ? A. 10 sec. C. 14 sec. Solution Speed of the train Time taken by it cover 220 m B. 12 sec. D. 16 sec. = (59 + 7) Kmph = (66 x 5/18) m/sec = (55 / 3 )m/sec = (220 x 3 /55)sec = 12 sec 41. Two stations A and B are 110 km apart on a straight line. One train starts from A at 7 a.m. and travels towards B at 20 kmph. Another train starts from B at 8 a.m. and travels towards A at a speed of 25 kmph. At what time will they meet ? A. 9 a.m B. 10 a.m
  12. PBI C. 10-30 a.m Solution Distance covered by A in x hours Distance covered by B in (x - 1) hours x = 3. So, they meet at 10 a.m PBI INSTITUTE 11 a.m D. = 20 x km = 25 (x - 1) km = + 25 (x - 1) = 110 = = 135 42. A train 108 m long moving at a speed of 50 km / hr crosses a train 112 m long coming from opposite direction in 6 seconds. The speed of the second train is A. 48km/hr C. 66km/hr Solution Relative speed Distance covered B. 54 km/hr D. 82km/hr = (x + 50) km/ hr + 50) x 5/18 m/sec = 250 + 5x/18]m/sec = (108 + 112) m = 220 m = 220 / (250 + 18) = 250 + 5 660 = 82 km / hr. 43. How long does a train 110 metres long running at the speed of 72 km / hr take to cross a bridge 132 metres in length ? A. 9.8 sec C. 12.42 sec Solution speed Total Distance covered Required time B. 12.1 sec D. 14.3 sec = (72 x 5/18 )m/sec = 20 m/ sec = (110 + 132) m = 242 m = (242 / 60) sec = 12.1 sec 44. In what time will a train 100 metres long cross an electric pole, if its speed be 144 km/hr ? A. 2.5 sec C. 5 sec Solution speed Time taken B. 4.25 Sec D. 12.5 sec = (144 x 5 / 18) m/sec = 40 m / sec = (100/40) sec = 2.5 sec. 45. A train 100 m long is running at the speed of 30 km/hr. Find the time taken by it to pass a man standing near the railway line.
  13. PBI A. Solution 10 sec. 14 B. D. PBI INSTITUTE 12 sec. 16 sec. Speed of the train Distance moved in passing the standing man Required time taken = (30 x 5/18)m/sec = (25 / 3) m/sec. = 100 m. x 3/ 25) sec = 12 sec. 46. A man sitting in a train which is travelling at 50 kmph observes that a goods train, travelling in opposite direction, takes 9 seconds to pass him. If the goods train is 280 m long, find its speed. A. 52 kmph. C. 72 kmph. Solution Relative Speed Speed of the train B. 62 kmph. D. 80 kmph. = (280 / 9)m/sec = (280/9 x 18/5) = 112 kmph. = (112 - 50)kmph = 62 kmph. 47. A train 150 m long is running with a apecd of 68 kmph. In what time will it pass a man who is running at 8 kmph in the same direction in which the train is going? A. 6sec. C. 9sec. Solution Speed of the train relative to man Time taken by it to cover 150 m at (50 /3)m/sec B. 7sec. D. lisec. 68-8) = 60 Kmph = 60 x 5/ 18 =50/3 m/sec. = (112 - 50)kmph = (150 x 3/50)sec = 9 sec. 48. A train moves with a speed of 108 kmph.lts speed in metres per second is A. 10.8 c. 30 Solution B. 18 D. 38.8
  14. PBI PBI INSTITUTE speed 49. = 108 Kmph = (108 x 5/18)m/sec = 30 m/sec. Two trains travel in opposite directions at 36 kmph and 45 kmph and a man sitting in slower train passes the faster train in 8 seconds. The length of the faster train is A. 80m C. 120m Solution Relative Speed Length of the train B. 100m D. 180m = (36 + 45) km/hr = (81 x 5/18) m/sec = (45/2) m/sec = (45/2 x 8) m = 180 m. 50. The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance traveled downstream in 12 minutes is A. 1.2 km C. 2.4 km Solution Speed downstreams Distance travelled B. 1.8 km D. 3.6 km =(15 + 3)kmph = 18 kmph. (18 x 12/60)km = 3.6km. 51. A boat takes 90 minutes less to travel 36 miles downstream than to travel the same distance upstream. If the speed of the boat in still water is 10 mph, the speed of the stream is A. 2 mph C. 3 mph Solution Speed downstreams Speed upstreams = 18 kmph. 36/(10-x) - 36/(10+x) B. 2.5 mph D. 4 mph =(10 + x)mph. =(10 - x)mph. = 90/60 = 90(100 - x= 2mph. 52. In one hour, a boat goes 11 km along the stream and 5 km against the stream. The speed of the boat in still water in ( km/hr) is B. D. 5 9 Solution Speed in still water = 1/ 2(11 5) km/hr
  15. PBI PBI INSTITUTE 53. = 8 km/ hr. A man can row three - quarters of a kilometer against the stream in Illkminutes. The speed(in km/hr) of the man in still water is Solution Rate upstream Rate downstream Rate in still water = (750 / 675)m/sec = (10 / 9) m/ sec. = (750 / 450) =(5 / 3) m/sec = 1/2(10 /9 + 5/3) = (25/18x18/5)km/hr = 5 km/hr. 54. If a man rows at the rate of 5 kmph in still water and his rate against the current is 3.5 kmph, then the man's rate along the current is A. 4.25 kmnph C. 6.5 kmph Solution Let the rate along the current be x kmph. Then, B. 6 kmph D. 8.5 kmph x= 6.5 kmph. 55. Speed of a boat in standing water is 9 kmph and the speed of the stream is 1. 5 kmph. A man rows to a place at a distance of 105 km and comes back to the starting point. The total time taken by him is A. 16 hours C. 20 hours Solution Speed upsteram Speed downsteram Total time taken B. 18 hours D. 24 hours = 7.5 kmph. = 10.5 kmph. 105/10.5]hours = 24 hours. 56. A boat covers a certain distance downstream in I hour, while it comes back in 11/2 hours. If the speed of the stream be 3 kmph. what is the speed of the boat in still Water? A. 12kmph C. 15kmph Solution B. 13kmph D. 16kmph Let the speed of the boat in still water be x kmph. Then, Speed downsteram Speed upsteram = (x + 3) kmph. = (x - 3) kmph. = (x+3)x1 = (x - 3)x3/2 kmph.
  16. PBI DREA Nas E PBI INSTITUTE 57. x= 15 kmph. A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr The man's speed against the current is A. 8.5 km/hr C. 10 km/hr Solution Man's rate in still water Man's rate against the current B. 9 km/hr D. 12.5 km/hr = (15 - 2.5) km/hr = 12.5 km/hr. = (12.5 - 2.5) km/hr = 10 km/hr. 58. A man can row upstream at 7 kmph and downstream at 10 kmph.Find man's rate in still water and the rate of current? A. 1.2 km/hr C. 1.6 km/hr Solution Rate in still water Rate of current B. 1.5 km/ hr D. 1.8 km/hr = 1/2 (10 + 7) km/hr = 8.5 km/hr. = 1/ 2(10 - 7) km/hr = 1.5 km/hr. 59. A boatman goes 2 km against the current of the stream in 1 hour and goes 1 km along the current in 10 minutes. How long will it take to go 5 km in stationary water? A. 40 minutes C. 1 hour 15 min Solution Rate downstream Rate upstream Speed in still water Required time B. 1 hour D. 1 hour 30 min = (1 / 10 x 60)km/hr = 6 km / hr. = 2 km/hr. = 1/ + 2)km/hr = 4 km. = (5 / 4) km/hr = lx 1/4 km/hr = 1 hr 15 min. 60. There is a road beside a river.Two friends started from a place A, moved to a temple situated at another place B and then returned to A again. One of them moves on a cycle at a speed of 12 km/hr, while the other sails on a boat at a speed of 10 km/hr. 1f the river flows at the speed of 4 km/hr, which of the two friends will return to place A first ? A. 5.4 km /hr C. 8.4 km/ hr Solution B. 7.2 km /hr D. 9.6 km /hr Clearly, the cyclist moves both ways at a speed of 12 km/hr. so, average speed of the cyclist Average speed = 12 km/hr. = (2x14x6114+6) km/hr = 42/5 kmph = 8.4 kmph
  17. PBI PBI INSTITUTE Since the average speed of the cyclist is greater, he will return to A first. 61. A boat can travel with a speed of 13 km / hr in still water. If the speed of the stream is 4 km / hr. find the time taken by the boat to go 68 km downstream? A. 2 hours C. 4 hours Solution Speed Downstream Time taken to travel 68 km downstream B. 3 hours D. 5 hours = (13 + 4) km/hr = 17 km/hr. / 17)hrs = 4 hrs. 62. The speed of a boat in still water is 15 km/hr and the rate of current is 3 km/hr. The distance travelled downstream in 12 minutes is A. 1.2 km C. 2.4 km Solution Speed Downstream Distance travelled B. 1.8 km D. 3.6 km = (15 + 3) km/hr = 18 km/hr. x 12/60)hrs = 3.6km. 63. A boat takes 19 hours for travelling downstream from point A to point B and coming back to a point C midway between A and B. If the velocity of the stream is 4 kmph and the speed of the boat in still water is 14 kmph, what is the distance between A and B? A. 160 km C. 200 km Solution Speed Downstream Speed upstream Let the distance b/w A and B be xkm.Then B. 180 km D. 220 km = (14 + 4) km/hr = 18 km/hr. - 4) km/hr = 10 km/hr.. / 10) = 19 = 180 = 19 180. 64. A boat running downstream covers a distance of 16 km in 2 hours while for covering the same distance upstream, it takes 4 hours. What is the speed of the boat in still water ? A. 4 km/hr C. 8 km/hr Solution Rate Downstream Rate upstream B. 6 km/ hr D. Data inadequate = (16/ 2) kmph = 8 kmph =(16 / 4) kmph = 4 kmph.
  18. PBI Speed in still water PBI INSTITUTE = 1/ 2 (8 + 4)kmph = 1/2 x 12 = 6 kmph. 65. A man can row upstream at 8 kmph and downstream at 13 kmph. The speed of the stream is A. 2.5 km/hr C. 5 km/hr Solution Speed of stream B. 4.2 km/hr D. 10.5 km/hr - 8 )kmph = 1/2 (13 = 2.5

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