Time And Distance
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A boat takes half time in moving a certain distance downstream than upstream. The ratio of the speed of the boat in still water and that of the current is
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2 : 1
-
1 : 2
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4 : 3
-
3 : 1
D.
3 : 1
Let the speed of the boat in still water be x kmph.
Speed of current be y kmph.
∴ Rate downstream = (x + y) kmph
Rate upstream = (x - y) kmph
Distance = Speed x Time
∴ (x - y) x 2t = (x + y) x t
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A bus travels 150 Km in 3 hours and then travel next 2 hours at 60 Km/hr. Then the average speed of the bus will be
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55 km/hr
-
54 km/hr
-
50 km/hr
-
60 km/hr
B.
54 km/hr
Total distance covered by the bus = (150 km + 2 x 60) km
= (150 + 120) km = 270 km
∴ Average speed
A car can finish a certain journey in 10 hours at the speed of 42 kmph. In order to cover the same distance in 7 hours, the speed of the car (km/h) must be increased by
-
12
-
15
-
18
-
24
C.
18
Distance covered by car = Speed x Time = 42 x 10 = 420 km.
New time = 7 hours
Thus, Required increase in speed = (60 - 42) kmph = 18 kmph
A car covers 
of the distance from A to B at the speed of 8km/hr, 
of the distance at 25 km per hour and the remaining at the speed of 20 km per hour. Find the average speed of the whole journey.
-
12.625 km/hr
-
13.625 km/hr
-
14.625 km/hr
-
15.625 km/hr
D.
15.625 km/hr
Let the total distance be 1 km.
∴ Total time 
A car covers four successive 7km distances at speeds of 10 km/hour, 20 km/hour, 30 km/hour and 60 km/hour respectively. Its average speed over this distance is
-
30 km/hour
-
20 km/hour
-
60 km/hour
-
40 km/hour
B.
20 km/hour
Total distance covered = 7 x 4 = 28 km
Total time taken
Average Speed
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Mock Test Series