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GWD 25 33 沒人問過

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楼主
发表于 2010-6-26 22:18:32 | 只看该作者 回帖奖励 |倒序浏览 |阅读模式
Q33.
A pump started filling an empty pool with water and continued at
a constant rate until the pool was full. At noon the pool was 1/3 full,
and 1+1/4 hours later it was 3/4 full. What was the total number of
hours that it took the pump to fill the pool?
A. 2+1/3
B. 2+2/3
C. 3
D. 3+1/2
E. 3+2/3

答案C

請問這題要如何解呢 ?
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沙发
发表于 2010-6-26 22:51:20 | 只看该作者
X is the totall water

so it takes 1+1/4 hours to finish (3/4-1/3) X water

(3/4-1/3)X/(1+1/4)=1/3 X water per hour

so the time to fill the pool is X/ (1/3 X)=3
板凳
发表于 2010-6-26 22:53:29 | 只看该作者
先用3/4减去1/3,即 5/4小时充了5/12的水, 用5/12除以5/4算出一小时可充满水池的1/3,所以三小时可以充满。这么说行吗?
地板
 楼主| 发表于 2010-7-5 11:01:42 | 只看该作者
hum 懂了  只要遇到這種題目 先算出一小時的單位量 對吧
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