Speed, Time and Distance
- If a train runs at 5/6 of its original speed, then it reaches the station 10 min late. Then find out the usual time taken by train to cover the distance.
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Assume the actual speed of train be x and actual time taken be y
And, distance is same in both caseCorrect Option: C
Let the actual speed of train be x and actual time taken be y
Then new speed of train = 5x/6
Therefore, new time taken = 6y/5 (as distance is same in both case)
Given, 6y/5 - y = 1/6 hr , therefore actual time = 50 min
- A car is moving with the speed of 47.52km/hr and the radius of the wheel of car is 21 cm. Calculate the approximate number of revolutions made by the wheel in one minute.
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Circumference of circle = 2πr
Where r = radius of circleCorrect Option: C
Speed in cm/minute = (Speed in km/hr x 1000 x100 )/60
= 47.52x(50/3)
=79200 cm/min
And Circumference of circle = 2πr
=2 x ( 22 / 7 ) x 21
=132
No. of revolutions = ( Speed in cm/minute ) / circumference of circle in cm
=79200 / 132
=600 rpm
- A man walking at 3km/hr crosses a square field diagonally in 2 min. The area of the field is ?
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speed = 3 x ( 5/18 ) m/sec.
= 5 / 6 m/sec.
∴ Distance covered in 2 min. = ( 5 / 6) x 2 x 60 m
= 100 m.
∴ Length of diagonal = 100 mCorrect Option: C
speed = 3 x ( 5/18 ) m/sec.
= 5 / 6 m/sec.
∴ Distance covered in 2 min. = ( 5 / 6) x 2 x 60 m
= 100 m.
∴ Length of diagonal = 100 m
Area of the field = 1/2 x diagonal2
=1/2 x 100 x 100 m2
= 5000 m2
= 50 acres.
- A certain distance is covered at a certain speed. If half of this distance is covered in double the time, the ratio of the two speed is ?
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Let x km . be covered in y hrs.
then, 1st speed = (x / y) km/hr.
2nd speed = [(x/2) / 2y)] km/hr.
= (x/4y) km/hr.Correct Option: A
Let x km . be covered in y hrs.
then, 1st speed = (x / y) km/hr.
2nd speed = [(x/2) / 2y)] km/hr.
= (x/4y) km/hr.
∴ Ratio of speed = x/y : x/4y = 1 :1/4 = 4: 1
- A is twice as fast as B and B is thrice as fact as C is . The journey covered by C in 42 minute, will be covered by A in ?
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Let C' s speed = x km/hr.
Then, B's speed = 3x km/hr.
and A's speed = 6x km/hr.
∴ Ratio of speed of A, B, C
= 6x : 3x : x = 6 : 3 : 1
Ratio of times taken = 1/6 : 1/3 : 1 or 1 : 2 : 6Correct Option: D
Let C' s speed = x km/hr.
Then, B's speed = 3x km/hr.
and A's speed = 6x km/hr.
∴ Ratio of speed of A, B, C
= 6x : 3x : x = 6 : 3 : 1
Ratio of times taken = 1/6 : 1/3 : 1 or 1 : 2 : 6
∵ 6 : 1 : : 42 : t
⇒ 6t = 42
⇒ t = 7 min.