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How many "+" added to the nine numbers below can make the result 99?(Adjacent n
How many "+" added to the nine numbers below can make the result 99?(Adjacent n
游客
2025-02-23
21
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问题
How many "+" added to the nine numbers below can make the result 99?
(Adjacent numbers can form a two-digit number)
123456789
选项
A、8
B、6
C、5
D、4
E、3
答案
B
解析
因为1+2+3+4+5+6+7+8+9=45,所以要使和为99,必须有相邻的两个数字构成两位数,但不能构成89,78,因为若构成这两个数,最后的和已经大于99。从67开始试验,1+2+3+4+5+67+8+9=99,共7个加号,但是答案中没有这个选项,67不行;
继续往下试验56,56+7+8+9=80,因此只要能够在1,2,3,4中加入加号,凑成和为19就行。12+3+4=19,所以12+3+4+56+7+8+9=99,共6个加号,B为正确答案。
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