Time and Distance Questions

FACTS  AND  FORMULAE  FOR  TIME  AND  DISTANCE

1.Speed = DistanceTime,  Time=DistanceSpeed, Distance= Speed×Time 

 

2. x km/hr = x×518 m/sec

 

3. x m/sec = x×185 km/hr

4. If the ratio of the speeds of A and B is a:b , then the ratio of the times taken by them to cover the same distance is or b : a

5. 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 2xyx+ykm/hr.

Q:

A son and father goes for boating in river upstream . After rowing for 1 mile son notices the hat of his father falling in the river. After 5 min he tells his father that his hat has fallen. So they turn round and are able to pick the hat at the point from where they began boating after 5min. Find the speed of river  in miles/hours ?

A) 4 mile/hr B) 6 mile/hr
C) 2 mile/hr D) 5 mile/hr
 
Answer & Explanation Answer: B) 6 mile/hr

Explanation:

Let the speed of river and boat be 'r' m/min and 'b' m/min.
so relative speed in upstream (b-r)m/min and in downstream (b+r)m/min.
Now in upstream distnce covered in 5 min is 5(b-r)miles
so total distnce covered => 1 + 5(b-r)miles in upstream
In downstream distance covered in 5min is 5(b+r)miles
Now 1 + 5(b-r) = 5(b+r)
1+5b-5r = 5b+5r
1 = 10r
r = 1/10 mile/min => 6 mile/hr.

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15 11605
Q:

Shahrukh starts from Barabanki to Fatehpur , 1 hour after Ajay starts. Shahrukh meets Kajol 1.5 hours after Shahrukh starts. If the speed of Shahrukh is at least 20km/h faster than the speed of Kajol.

What is the minimum speed of Shahrukh to overtake Ajay, before he meets Kajol?

A) 30 B) 40
C) 60 D) None of these
 
Answer & Explanation Answer: D) None of these

Explanation:

Let t be the time after Kajol starts, when she meets Ajay, then 

               t = 300/(x+y) 

 This should be less than 2.5 or (x+y)>120 

Since       y= 3x/2  =>  y > 72

This (y>72) is greater than 67.5 km/h and hence Shahrukh will always overtake Ajay before he meets Kajol.

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21 11514
Q:

A train with 120 wagons crosses Arun who is going in the same direction, in 36 seconds. It travels for half an hour from the time it starts overtaking the Arun ( he is riding on the horse) before it starts overtaking the Sriram( who is also riding on his horse) coming from the opposite direction in 24 seconds. In how much time (in seconds) after the train has crossed the Sriram do the Arun meets to Sriram?

A) 3560 sec B) 3600 sec
C) 3576 sec D) can't be determined
 
Answer & Explanation Answer: C) 3576 sec

Explanation:

Let the length of the train be L metres and speeds of the train Arun and Sriram be R, A and S respectively, then 

       LR-A=36 ---------- (i) 

and LR+K=24 ---------(ii)

 

From eq.(i) and (ii)

              3(R - A ) = 2 (R + K) 

  R = 3A + 2K 

 

In 30 minutes (i.e 1800 seconds), the train covers 1800R (distance) but the Arun also covers 1800 A (distance) in the same time. Therefore distance between Arun and Sriram, when the train has just crossed Sriram

               = 1800 ( R - A) - 24 ( A + K)

 

 Time required = 1800(R-A)-24(A+K)(A+K)

 

= (3600 - 24) = 3576 s                            

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34 11308
Q:

Ashwin fires two bullets from the same place at an interval of 15 minutes but Rahul sitting in a bus approaching the place hears the second sound 14 minutes 30 seconds after the first. If sound travels at the speed of 330 meter per second, what is the approximate speed of bus?

A) 330/29 m/s B) 330 x 30 m/s
C) 330/14 m/s D) 330/900 m/s
 
Answer & Explanation Answer: A) 330/29 m/s

Explanation:

Second gun shot take 30 sec to reach rahul imples distance between two.

given speed of sound = 330 m/s

Now, distance = 330 m/s x 30 sec 

 

Hence, speed of the bus = d/t = 330x30/(14x60 + 30) = 330/29 m/s.

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24 11275
Q:

Amy has to visit towns B and C in any order. The roads connecting these towns with her home are shown on the diagram. How many different routes can she take starting from A and returning to A, going through both B and C (but not more than once through each) and not travelling any road twice on the same trip?

A) 10 B) 8
C) 6 D) 4
 
Answer & Explanation Answer: B) 8

Explanation:

Amy can travel clockwise or anticlockwise on the diagram.

Clockwise, she has no choice of route from A to B, a choice of one out of two routes from B to C, and a choice of one out of two routes from C back to A. This gives four possible routes.

Similarly, anticlockwise she has four different routes.

Total routes = 8

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31 11221
Q:

Arjun and Bhishma are running on a circular track of length 600m. Speed of Arjun is 30 m/s and that of Bhishma is 20 m/s .They start fro the same point at the same time in the same direction. When will they meet again for the first time?

Answer

SolTime = Circumference Relative Speed = 60010 = 60 sec.


 


Actually Arjun has to make a lead of 600 m, because when Arjun will be 600m ahead of Bhishma, they will be together again as a person when completes the total length it starts retracing he same path and thus Arjun and Bhishma can be together again.


 


Since , they make  a difference of 10 m in 1 second. so, he will create 600m difference in 60 second.

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14 11220
Q:

A train of length 250 m crosses a bridge of length 150m in 20 seconds. What is the speed of train?

Answer

Sol : (length of train+ length of bridge) = speed of train x Time


        (250+150) = 20 x Speed


        Speed = 400/20= 20 m/s =72 km/h

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8 10982
Q:

A and B runs around a circular track. A beats B by one round or 10 minutes. In this race, they had completed 4 rounds. If the race was only of one round, find the A's time over the course:

A) 8 min B) 7.5 min
C) 12.5 min D) 12 min
 
Answer & Explanation Answer: B) 7.5 min

Explanation:

B runs around the track in 10 min.

 i.e ,    Speed of B = 10 min per round

 Therefore,  A beats B by 1 round

  Time taken  by A to complete 4 rounds 

  = Time taken by B to complete 3 rounds  

 = 30 min 

 

Therefore, A's speed = 30/4 min per round = 7.5 min per round

 Hence, if the race is only of one round A's time over the course = 7 min 30 sec

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