2017年河南郑州豫才杯六年级竞赛
某学校准备购买$$30$$个篮球，三家商店每个篮球的售价都是$$25$$元，但优惠方法不同，$$A$$店``买九赠一''，$$B$$店``打八八折''；$$C$$店``满$$100$$元减现金$$10$$元''，为节约资金，应该到店购买．  A school is going to buy 30 basketballs. The price of each basketball in the three stores is 25 yuan, but the preferential methods are different. Store A "buy nine and get one free", store B "give a 20\% discount";~Store C ~"full 100 yuan minus 10 yuan in cash", in order to save money, should go to store to buy. 
拓展思维->思想->对应思想
甲店：只需付$$27$$个篮球的钱即可买到$$30$$个篮球，要$$27\times 25=675$$元；  乙店：$$30\times 25\times 88  \% =660$$元；  丙店：$$25\times 30=750$$元，减$$7\times 10=70$$元，花费$$750-70=680$$元．  因为$$660\textless{}675\textless{}680$$，所以应到乙店购买． 