One snail climbed from the bottom of a well that was 10m deep. It climbed up 4m during the day, and slid down 2m during the night. Which day could the snail climb out of the well?  $4-2=2$  $10\div2=5$  The 5th day. 
Overseas Competition->Knowledge Point->Word Problem Modules->Periodic Problems->Snail Climbing out of Well Problems