Problema Solution
A worm is at the bottom of a 12-foot wall. Every day the worm crawls up 3 feet, but at night it slips down 2 feet. How many days does it take the worm to get to the top of the wall?
Answer provided by our tutors
net gain each day is 3-2=1 foot until the first time the worm reaches the top of the wall, which will happen when slippage would have taken the worm back to 10 feet
so the worm needs to firmly reach the 9-foot mark on the final day of climbing and then on the next day the top will be reached [and presumably no more slippage will occur because the worm is on top!]
9 feet / (1foot/day) = 9 days
9+1 = 10
the worm will reach the top on the 10th day