以下的我都不懂得做
P.S in englih
1)The ages of Amy and Billy are in the ratio 2:3. If Billy is 6 years older than Amy, how old are Amy and Billy respectively?
2)It is given that x: y = 2:1 and y: z = 3:1
If x+y+z = 40, find the value of y.
有些數學問題不懂做（中二級）用英文的
2013-01-01 10:44 pm
回答 (1)
2013-01-01 11:11 pm
✔ 最佳答案
1) Let A be the ages of Amy , B be the ages of Billy :A : B = 2 : 3 ... (1)A + 6 = B ... (2)Sub. (2) into (1) :
A : (A + 6) = 2 : 3
2(A + 6) = 3A
A = 12
B = 12+6 = 18Amy is 12 years old.
Billy is 18 years old.
2)x : y = 2 : 1 = 6 : 3
and
y : z = 3 : 1 ∴ x : y : z = 6 : 3 : 1x + y + z = 40
6z + 3z + z = 40
10z = 40
z = 4
∴ y = 3*4 = 12
收錄日期: 2021-04-21 22:28:10
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20130101000051KK00143