GMAT
题目
The rainfall in City M during May of last year was 3 times the average (arithmetic mean) monthly rainfall for the other 11 months of last year. If the average monthly rainfall for last year was 3.5 inches, what was the rainfall, in inches, in City M during May?
解析
设月平均降雨量为\(a\)。
该年的总降雨量 = 11个月的降雨量 + \(M\)月的降雨量，因此有：
\[
\begin{align*}
3.5×12 &= 11×a + 3×a \\
42 &= 14a \\
a &= 3
\end{align*}
\]
\(M\)月的降雨量 = \(3a = 3×3 = 9\)
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