Prep-Test2-DS-139

[chris8888]

139. 14556-!-item-!-187;#058&010396
If machine J, working alone at its constant rate, takes 2 minutes to wrap 60 pieces of candy, how many minutes does it take machine K, working alone at its constant rate, to wrap 120 pieces of candy?

(1) Machine K, working alone at its constant rate, takes more than 5 minutes to wrap 60 pieces of candy.

(2) Machines J and K, working together at their respective constant rates, take 1 minute and 30 seconds to wrap 60 pieces of candy.

[小花]

139. 14556-!-item-!-187;#058&010396
If machine J, working alone at its constant rate, takes 2 minutes to wrap 60 pieces of candy, how many minutes does it take machine K, working alone at its constant rate, to wrap 120 pieces of candy?

(1) Machine K, working alone at its constant rate, takes more than 5 minutes to wrap 60 pieces of candy.

(2) Machines J and K, working together at their respective constant rates, take 1 minute and 30 seconds to wrap 60 pieces of candy.

我選D
查答案竟是B
真是怪 (1)位什麼 不行

[chris8888]

139. 14556-!-item-!-187;#058&010396
If machine J, working alone at its constant rate, takes 2 minutes to wrap 60 pieces of candy, how many minutes does it take machine K, working alone at its constant rate, to wrap 120 pieces of candy?

(1) Machine K, working alone at its constant rate, takes more than 5 minutes to wrap 60 pieces of candy.
只說K花超過5分鐘去包裝60個糖果包. insufficient
無法計算出每分鐘可以包裝幾個, 需要計算平均的包裝速度.

(2) Machines J and K, working together at their respective constant rates, take 1 minute and 30 seconds to wrap 60 pieces of candy.
以前做的這種題型都不是這種計算法, 突然改一下還真的給他反應不過來
獨自運轉, 表示每一台機器都會花掉1分30秒,
60/2 = 30 pieces / 1 minute J
假設K, X pieces / 1 minute
30 * 1.5分鐘 + X * 1.5分鐘 = 60
X = 10 pieces / 1 minute

120 pieces / 10 pieces = 12 minutes

Answer : B

我終於想通了, 真是豬頭.