JJ 问题

hytseng

16、DS
The number of boys in a class and the number of the total of boys and girls who take the course of biology is shown in the form blew, How many is all the boys and girls in the class.

表格

boy 28

girl

total 36

1. There are 3 boys who do not take biology
2. The girls in the class is twice as many as the totle of boys and girls who do not take biology

C
一直算不出来 ， 觉得是 E

4. To go a 405 miles trip, a car can go 36 miles per gallon for gasoline A , and for gasoline B, the efficiency decreased by 1/3 of A, ask during this trip, the car can save how many gallon of gasoline A for whole trip than it uses gasoline B?
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405/72

我的算法
405/12 - 405/36 = 22.5



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[此贴子已经被作者于2002-10-18 14:53:03编辑过]

[此贴子已经被作者于2002-10-18 14:54:04编辑过]

Kilroy

选C
设总共GIRL为X人，NO-BIOLOGY GIRL为Y人
X=2（3+Y）
36-（28-3）+Y=X
得出X=16人，总人数为16+28=44人

michaelwu64

4.我想“....the efficiency decreased by 1/3 of A” 的意思应是(1-1/3)*36=24。所以妳的算式应修正为405(1/24-1/36)=405/72

ruthy_yin

16选B,我在以前的贴子里和tongxun讨论过
x=2(x+28-36) => x=16

hytseng

ruthy_yin...
x=2(x+28-36) ??
What does X stand for ?　

Kilroy

为什么可以X2？