Problem: A snail crawls slowly up a garden wall 48cm high. If it crawls forward 8cm a day and slips back 3cm each night, how long will it take to arrive at the top of the wall?
Solution: It will take nine days. If it travels 8cm forward and 3cm back during each 24-hour period then it progresses at a rate of 5cm a day. After 8 days it will have reached 40cm but slips back 3cm. On the ninth day it will have reached the top before slipping back.