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.

 40 min
 45 min
 50 min
 55 min

View Hint View Answer Discuss in Forum
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.

 250 rpm
 200 rpm
 600 rpm
 300 rpm

View Hint View Answer Discuss in Forum
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 ?

 25 acres
 30 acres
 50 acres
 60 acres

View Hint View Answer Discuss in Forum
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 diagonal^{2}
=1/2 x 100 x 100 m^{2}
= 5000 m^{2}
= 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 ?

 4:1
 1.4
 2:1
 1:2

View Hint View Answer Discuss in Forum
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 ?

 14 min
 28 min
 63 min
 7 min

View Hint View Answer Discuss in Forum
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.