A train passes an electrical pole in 20 seconds and passes a platform 250 m long in 45 seconds. Find the length of the train:

Let the length of the train = L

Length of the platform (l) = 250 m

The train passes the electrical pole in 20 seconds

$$\therefore\ $$Speed of the train = $$\frac{L}{20}$$ m/sec

The train passes the platform in 45 seconds

$$\therefore\ $$Speed of the train = $$\frac{L+250}{45}$$ m/sec

$$=$$>  $$\frac{L}{20}=\frac{L+250}{45}$$

$$=$$>  $$\frac{L}{4}=\frac{L+250}{9}$$

$$=$$>  $$9\text{L}=4\text{L}+1000$$

$$=$$>  $$5\text{L}=1000$$

$$=$$>  $$\text{L}=$$ 200 m

$$\therefore\ $$Length of the train = 200 m

Hence, the correct answer is Option C