99个苹果装进两种包装盒,大包装盒每盒装12个苹果,小包装盒每盒装5个苹果,共用了十多个盒子刚好装完。问两种包装盒相差多少个?A.3 B.4 C.7 D.13

作者: tihaiku 人气: - 评论: 0
问题 99个苹果装进两种包装盒,大包装盒每盒装12个苹果,小包装盒每盒装5个苹果,共用了十多个盒子刚好装完。问两种包装盒相差多少个?
选项 A.3 B.4 C.7 D.13
答案 D
解析 设有大包装盒x个,小包装盒y个,根据题意可知,12x+5y=99。由奇偶性可知,5y必为奇数,即y为奇数,则5y的尾数只能是5,此时12x的尾数是4,x=2或7。当x=2时,y=15,符合题意,故两种包装盒相差15-2=13个。(当x=7时,y=3,此时x+y=10,不符合“共用了十多个盒子”的要求)

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