PP-T1-PS40

[Huang Hsin-Yi]

40. 5629-!-item-!-187;#058&004684
Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?

(A) 2
(B) 3
(C) 4
(D) 6
(E) 8


Ans:B

[amyliang]

速率 * 時間 = 工作量
M * 12 = 1 所以六台機器的速率為1/12 一台就是1/72
(1/72)X * 8 = 1
X = 9 需要九台機器 所以比原本多三台

[Huang Hsin-Yi]

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