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  3. In the first 2 hours after Meadow’s self-service laundry opens, m large washing

In the first 2 hours after Meadow’s self-service laundry opens, m large washing

游客2025-02-27  14
问题 In the first 2 hours after Meadow’s self-service laundry opens, m large washing machines and n small washing machines are in continual use. Including the time for filling and emptying the washing machines, each load of laundry takes 30 minutes in a large washing machine and 20 minutes in a small washing machine. What is the total number of loads of laundry done at Meadow’s self-service laundry during this 2-hour period?
(1) n = 3m
(2) 2m + 3n = 55
选项 A、Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B、Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C、BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D、EACH statement ALONE is sufficient.
E、Statements (1) and (2) TOGETHER are NOT sufficient.
答案 B
解析 During the two-hour period each large washer does four loads (the number of 30-minute periods in two hours is four) and each small washer does six loads (the number of 20-minute periods in two hours is six).Therefore, the total number of loads done during the two-hour period by m large washers and n small washers is Am + 6n.
(1)    If m = l and n = 3, then n = 3m and the total number of loads of laundry done in the two-hour period is 4(1) + 6(3) = 22. However, if m = 2 and n = 6, then n = 3m and the total number of loads of laundry done in the two-hour period is 4(2) + 6(6) = 44; NOT sufficient.
(2)    Since 2m + 3n = 55, it follows that 4m + 6n = 110. Therefore, by the remarks above, the total number of loads done during the two-hour period is 110; SUFFICIENT.
The correct answer is B;
statement 2 alone is sufficient.
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