A snail falls down a ten-meter well.It climbs three meters by day.But it slides down two meters at night.How many days can it climb out of the well?
A snail falls down a ten-meter well.It climbs three meters by day.But it slides down two meters at night.How many days can it climb out of the well?
一只蜗牛落进十米深的井中，它白天爬上三米，夜间滑下两米．要多少天才能爬出井口？