Mathematics Question on Time Speed and Distance

Question

A man in a train notices that he can count 21 telephone posts in one minute. If they are known to be 50 metres apart, then at what speed is the train travelling

Answer 1

Solution

The correct option is (B): 60km/h
To find the speed of the train, let's break down the problem:

- Number of posts counted = 21
- Distance between each post = 50 meters

Step 1: Calculate the total distance covered in one minute
- If there are 21 posts, the train has passed through 20 gaps between the posts (since the distance between the posts is counted, not the posts themselves).
- The total distance covered in 1 minute is:
$\text{Distance} = 20 \times 50 = 1000 \text{ meters}$

Step 2: Convert the distance covered in one minute to kilometers per hour
- Distance covered in one minute = 1000 meters = 1 kilometer
- Since 1 minute is $\frac{1}{60}$ of an hour, the speed of the train in kilometers per hour (km/h) is:
$\text{Speed} = 1 \text{ kilometer} \times 60 = 60 \text{ km/h}$

Conclusion: The speed of the train is 60 km/h.