GMAT(Problem Solving)対策問題

Q.08

Yesterday, a ship sailed from port A to port B at an average speed of 50 kilometers per hour.
Returinig from port B to port A in a same climate condition, the ship was travelling at 40.
If it takes 2 hour longer to return from port B to port A than to sail from port A to port B, how many kilometers did the ship travel each way?

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