Adam and Brianna plan to install a new tile floor in a classroom

题目

Adam and Brianna plan to install a new tile floor in a classroom. Adam works at a constant rate of 50 tiles per hour, and Brianna works at a constant rate of 55 tiles per hour. If the new floor consists of exactly 1400 tiles, how long will it take Adam and Brianna working together to complete the classroom floor?

选项

26 hrs. 44 mins.

26 hrs. 40 mins.

13 hrs. 20 mins.

13 hrs. 18 mins.

12 hrs. 45 mins.

解析

亚当的工作效率 = 50块瓷砖/小时布里安娜的工作效率 = 55块瓷砖/小时两人合作效率 = 105块瓷砖/小时完成1400块瓷砖所需的时间为： \[ \frac{1400}{105} = \frac{40}{3} = \frac{39}{3} + \frac{1}{3}×60 = 13小时20分钟 \] 答案：C

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