问答题

While working on a case Dr Watson accidentally fell down a 30ft dry wishing well. Sherlock Holmes lowered him down a rope. "Can you climb up" shouted Holmes. "I’ll be out before you know it. " came Watson’s reply. But the climb wasn’t as easy as Watson had first imagined. Each hour he managed to climb 3ft--but slipped back 2ft.
How long did it take Watson to get out