一題 f1數

👨🏻‍🏫 學術台數學

[匿名]

2009-02-18 5:54 am

There are 36 students in S1B. Some of them bring their own lunch and the others buy lunch boxes. If 1/5 (5分之一) of the students who usually bring their own lunch buy lunch boxes today , the ratio of students bringing their own lunch to those buying lunch boxes will be 1:2 .
How many students are there who usually bring their own lunch ?

更新1:

哦` 可以既v3v 等我1陣我翻譯作中文

更新2:

唔想用方程- -v` 唔用方程應該計到架

回答 (1)

用戶2053

2009-02-18 6:04 am

✔ 最佳答案

Let x students are there who usually bring their own lunch :

then 4/5 * x : (36 - 4/5 * x) = 1 : 2

2*4/5*x = 36 - 4/5 * x

3*4/5*x = 36

4/5x = 12

x=15

There are 15 students who usually bring their own lunch.

2009-02-17 22:12:59 補充：
不用方程:
有36人,今天自帶比買=1:2

即自帶有36/3*1=12人
買有24人

由於12是平時少五分一,平時有12/0.8=15人

係咪o甘?

參考: ME

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