GMAT
题目
Printing press X can print an edition of a newspaper in 12 hours, whereas press Y can print the same edition in 18 hours. What is the total number of hours that it will take the two presses, working together but independently of one another, to print the same edition?
解析
X的工作效率：\(\frac{1}{12}\)
Y的工作效率：\(\frac{1}{18}\)
合计效率：\(\frac{1}{12} + \frac{1}{18} = \frac{5}{36}\)
所需时间：\(\frac{36}{5} = 7.2\) 小时
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