CAT 1993 — QA Question 47

The separation between the ship and the seaplane is 18 miles. 

Since the two are travelling in the same direction, the relative speed would be 9 times the speed of the ship (If speed of ship is x miles/hour, speed of the seaplane would be 10x and 10x – x = 9x). 

Hence, to catch up with the ship, the seaplane would take $\frac{18}{9x}=\frac{2}{x}$ hours. 

Now, the ship covers x miles in an hour, so in $\frac{2}{x}$ hours it would cover 2 miles. 

So when the seaplane catches up with the ship, it would be 18 + 2 = 20 miles from the shore.

Hence, option (d).