A worm is at the bottom of a well with a depth of $$11$$ metres. If it climbs up $$3$$ metres in the day and slips down $$1$$ metre at night, how many days will it take the worm to climb up to the ground? 
Overseas Competition->Knowledge Point->Word Problem Modules->Periodic Problems->Snail Climbing out of Well Problems
It climbs up $$3$$ meters in the day time and slips down $$1$$ meter at night, so it climbs up $$2$$ meters in a whole day. For the first $$4$$ days, it climbs $$8$$ meters. During the day time of the fifth day, it climbs $$3$$ meters and reaches the ground. Then it needs five days to climb up to the ground. 