A train speeds past a pole in 20 seconds and speeds past a platform 100 meters in length in 30 seconds. What is the length of the train?

A. 100 meters

B. 150 meters

C. 180 meters

D. 200 meters

Answer: Option D

Solution(By Examveda Team)

Let the length of the train be x meters and its speed be y m/sec.
Then, $$\frac{{\text{x}}}{{\text{y}}}$$ = 20
⇒ y = $$\frac{{\text{x}}}{{20}}$$
∴ $$\frac{{{\text{x}} + 100}}{{30}}$$  = $$\frac{{\text{x}}}{{20}}$$
⇒ 30x = 20x + 2000
⇒ 10x = 2000
⇒ x = 200 meters