david bought 100 rubbers for $200 .he sold 30% of them at a price of $4 each and then sold the remaining rubber at $3 ea
问题描述：
david bought 100 rubbers for $200 .he sold 30% of them at a price of $4 each and then sold the remaining rubber at $3 each .find the percentage change.
答
the total money he get from solding all rubbers=30*4+70*3=$330
so the changed percentage=330/200=165%