请教一题

chengxiao88

a mixture is composed of 5 gallons of water and 2 gallons of antifreeze. now use 7 gallons of the mixture and add 3 gallons of antifreeze to the mixture. what is the percentage of antifreeze in the mixture?答案为65%。请帮忙解释一下！谢谢！！

himba

我们只要考虑最后的混合物中water有5gallons，antifreeze有2（原来混合物中的）+3（新增加的）gallons，那么antifreeze的百分比为5/10，
应该是50%，怎么是65%，答案是哪里的啊？