X and Y are two station 500 km apart. A train start from X and moves toward Y at 20 km/hr another train station from Y at the same times and moves toward X at 30 km/hr. How far from X will they cross each other?
Correct Answer: 200 km.
Explanation:
Suppose they meet x km. from X
Then, x/20 = (500 - x)/30
⇒ 30x = 10000 - 20x
∴ x = 200 km.