pp-t1-ps-145

[pauline_chiou]

145. 15048-!-item-!-187;#058&010243
Each of 10 machines works at the same constant rate doing a certain job. The amount of time needed by the 10 machines, working together, to complete the job is 16 hours. How many hours would be needed if only 8 of the machines, working together, were used to complete the job?

(A) 18
(B) 20
(C) 22
(D) 24
(E) 26

請問這要怎麼算呢

[nemolee]

十台機器共同完成1份工作
S x Hours = 1
S * 16 = 1, 則 S = 1/16 (十台的速率) ，1台的速率 = 1/160

題目，今天只要用8台機器，則需要多少時數?
(1/160) X 8 X H = 1 , H = 20

選B

[pauline_chiou]

感謝!!!
忘記去算1台的速率@@