GMAT
题目
A chemical factory produces two kinds of unnatural amino acids: acid A and acid B. Of the acids produced by the factory last year, were acid A and the rest were acid B. If it takes as many hours to produce acid B per unit as it does to produce acid A per unit, then the number of hours it took to produce the acid B last year was what fraction of the total number of hours it took to produce all the acids?
解析
这个问题本质是求酸A和酸B的生产时间，进而计算两者生产时间的关系。
计算生产酸A所用的时间：
\(\frac{1}{3} × \frac{5}{5} = \frac{5}{15}\)
计算生产酸B所用的时间：
\(\frac{2}{3} × \frac{2}{5} = \frac{4}{15}\)
将酸A和酸B的生产时间相加：
\(\frac{5}{15} + \frac{4}{15} = \frac{9}{15}\)
计算酸B的生产时间与总生产时间的比值：
\(\frac{4}{15} ÷ \frac{9}{15} = \frac{4}{15} × \frac{15}{9} = \frac{4}{9}\)
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