# CLASS-7PROBLEM & SOLUTION OF TIME-SPEED-DISTANCE

Problem Solving Example

1)  If a train cross the 150 km in just 3 hours then find the speed in km/h

Ans.)    If, a train takes 3 hours covers 150 km

By,  1 hours =  150/3   =  50 km/h      (Ans.)

2) If a train’s speed is 60 Km/h then this train how far will go by 5 hours ?

Ans.)  If, train in 1 hour can cross or cover 60 km distance

By 5 hours train can cross or cover = 60 Km X 5 h = 300 Km   (Ans.)

3) If a train cross 200 meters in 10 minutes then what is the speed of this train ?

Ans.) As we know that, the speed of train can be measured according to per hour basics

So, by 10 minutes train cross 200 miters

1 minutes train cross  200 ÷ 10 = 20 miters

Then by, 1 hour = 60 minutes  train cross 20 X 60 = 1200 miters

=  1200 meters/1000 meters = 1.20 km

So, the speed of the said train is 1.20 Km/h      (Ans.)

4) The speed of a car is 45 Km/h, find it’s speed in m/s.

Ans.) As we all know 1 Km = 1000 m

So, 45 Km = 45000 m

1 Hour  =  60 minutes

1 minutes = 60 seconds

So, 1 hour = 60 X 60 = 3600 seconds

So, if the car by 3600 seconds can move 45000 meters

1 second = 45000 / 3600 = 12.5 meters/s     (Ans.)

5) If a train takes 6 hours to complete a journey at a speed of 72 km/h, how long will another train take to complete the same journey if it’s speed is 15 m/s.

Ans.) as per the given condition the second train speed is  15 m/s

So, now we have to convert the speed via Km/h

15 m = 15 / 1000 = 0.015 Km (as we know that, 1000 miters = 1 Km)

So, if the train by 1 second can cross = 0.015 Km

3600 seconds can cross = 0.015 X 3600 = 54 Km/h

Now, If the first train by 1 hour can cross 72 km

Then, by 6 hours can cross  = 72 X 6 = 432 km

If the other train can cross 54 Km by 1 hour

Then, can cross 1 Km by  1/54 hour

432 km can cross by = 432 / 54 = 8 hours

So, the second train will take 8 hours to achieve the same distance that the first train has covered.           (Ans.)