A train speeds past a pole in 15 seconds and a platform 100 m long in 25 seconds. Its length is:50 m150 m200 mData inadequate

To solve this problem, we first need to understand that when a train crosses a pole or a person standing on a platform, the distance covered by the train is equal to the length of the train itself.

Step 1: So, if the train takes 15 seconds to cross a pole, that means the length of the train is the distance it can travel in 15 seconds.

Step 2: Next, when the train crosses a platform, the distance covered is the length of the train plus the length of the platform.

Step 3: We know that the train takes 25 seconds to cross a platform that is 100m long. So, the distance the train can travel in 25 seconds is the length of the train plus 100m.

Step 4: Now, we can set up an equation to solve for the length of the train. Let's denote the length of the train as 'L'.

From step 1 and step 3, we can say that: The distance the train travels in 15 seconds = L The distance the train travels in 25 seconds = L + 100m

Step 5: Since the speed of the train is constant, the distances it travels in 15 seconds and 25 seconds are proportional to the times. So, we can write the equation as: L/15 = (L + 100)/25

Step 6: Solving this equation will give us the length of the train.

So, the length of the train is 150m.