PP-T2-PS140

[little8]

140. 13512-!-item-!-187;#058&010037
A farm used two harvesting machines, H and K, to harvest 100 acres of wheat. Harvesting machine H, working alone at its constant rate, harvested 40 acres of wheat in 8 hours. Then harvesting machine K was brought in, and harvesting machines H and K, working together at their respective constant rates, harvested the remaining acres of wheat in 5 hours. Harvesting machine K harvested how many acres of wheat per hour?

(A) 7
(B) 8
(C) 12
(D) 13
(E) 15

Ans:A

[Huang Hsin-Yi]

由題目得知

machine H speed= 40/8hour=5 acre/hour

then machineH+J work 60acre
設J speed X acre/hour

therefore 60/5+x=5hour
x=7 acre/hour


1.工作量/時間= 速度
2.當兩台機器一起工作時,記得速度相加