AMC 8 1994 Problem 8

AMC8 1994 年第 8 题

特殊数与不定方程★★☆☆☆

For how many three-digit whole numbers does the sum of the digits equal 25 ?

有多少个三位正整数，其各位数字之和等于 25？

A.2
B.4
C.6
D.8
E.10

正确答案 · Correct Answer

解析 · Solution

Solution 1

Because 8+8+8=24, it follows that one of the digits must be a 9. The other two digits them have a sum of 25-9=16. The groups of digits that produce a sum of 25 are 799, 889 and can be arranged as follows

$799,979,997,889,898,988$

The number of configurations is

\text{(C)6}

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