题目

Using too much water or throwing rubbish into our rivers are clear ways that humans can put our water supply in danger ,but we also affect our water supply in less obvious ways .    You may wonder how paving(铺砌) a road can lead to less useable fresh water . A major part of the water we use every day is groundwater . Groundwater does not come from lakes or rivers .It came from underground . The more roads and parking lots we pave ,the less water can flow into the ground to become groundwater .     Human activity is not responsible for all water shortages(短缺). Drier climates周末，小明骑自行车从家里出发到野外郊游．从家出发0.5小时后到达甲地，游玩一段时间后按原速前往乙地．小明离家1小时20分钟后，妈妈驾车沿相同路线前往乙地，如图是他们离家的路程y（km）与小明离家时间x（h）的函数图象．已知妈妈驾车的速度是小明骑车速度的3倍． （1）求小明骑车的速度和在甲地游玩的时间； （2）小明从家出发多少小时后被妈妈追上？此时离家多远？ （3）若妈妈比小明早10分钟到达乙地，求从家到乙地的路程．