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Time and Distance

Time and Distance - Important Points


1.

In what time an athlete can cover a distance of 500 m if he runs at a speed of 36 kmph?

A. 50 seconds

B. 55 seconds

C. 72 seconds

D. 80 seconds

Discuss Work Space

Answer: option a

Explanation:

Speed given = 36 kmph = 36 x 5 /18 m/sec = 10 m/sec

Distance to be covered = 500 m

Time taken = Distance / speed = 500 / 10 = 50 secs


2.

A train travels from City A to City B at a speed of 44 kmph, while on its return journey, it was travelling at speed of 77 kmph. The average speed (in Kmph) of the train is:

A. 56

B. 58.5

C. 60

D. 60.5

Discuss Work Space

Answer: option a

Explanation:

Let x be the speed of the train while going from City A to B.
Let y be the speed of the train while going from City B to A.

Average speed of the train is given by = 2xy / (x+y)
Average speed = (2 x 44 x 77) / (44 + 77 )
Average speed = 56


3.

A bus travels from City X to City Y at a speed of 32 kmph, while on its return journey, it travels at the speed of 96 kmph. Find the average speed of the bus (in kmph).

A. 64

B. 58

C. 48

D. 44

Discuss Work Space

Answer: option c

Explanation:

Let x be the speed of the bus while going from City X to Y. Let y be the speed going from City Y to X.
Average speed of the bus is given by = 2xy / (x+y)
Average speed = (2 x 32 x 96) / (32 + 96 )
Average speed = 48


4.

A car completes journey in 10 hrs, the first half at 21 kmph and the second half at 24 kmph. The distance covered (kms) is: 

A. 224

B. 214

C. 234

D. 204

Discuss Work Space

Answer: option a

Explanation:

Let the distance to be covered be x km
Then x/2 km is travelled at a speed of 21 kmph and x/2 at 24 kmph

Time taken to covered whole journey is 10 hrs
=> x / (2 x 21) + x / (2 x 24) = 10
=> x / 42 + x / 48 = 10
=> 48x + 42x = 42*48*10
=> x = (42*48*10) / 90
=> x = 224
Distance covered = 224 km


5.

A person travels from city A to city B. During his onward journey his speed was 12 kmph and while returning his tripled his speed. His average speed (in kmph) is: 

A. 18

B. 22

C. 24

D. 36

Discuss Work Space

Answer: option a

Explanation:

Speed of backward journey = 36 kmph
Average Speed = 2*12*36 / (12 + 36)
              = 18 kmph