一元一次方程
回答 (3)
2006-11-26 7:41 am
✔ 最佳答案
其實要答對這種問題,要訣係先設定一個未知數.我習慣把較小的那個數設定為x所以在這條問題中,便把小文現在的年齡設定為x
由於小文爸爸現在的年齡係小文的4倍,所以小文爸爸現在的年齡就係4x
而在五年前,小文的年齡就係x-5,而小文爸爸五年前的年齡係小文的7倍,即係7(x-5)
所以4x-5=7(x-5)
4x-5=7x-35
30=3x
x=10
所以小文現在的年齡係10歲,而小文爸爸現在的年齡就係4(10)=40歲
參考: 自己
2006-11-26 10:01 am
Let Y is age of father and X is age of son.
Today:
ratio is 4
4 = (Y/X), Y = 4X ................(1)
Five years ago:
ratio is 7
7 = (Y-5) / (X-5)
7(X-5) = (Y-5)
7X-35 = Y-5 ........................(2)
(1) in (2)
7X-35 = 4X -5
3X = 30
X = 10 and Y = 40
therefore
Father is 40 years and son is 10 years today.
Today:
ratio is 4
4 = (Y/X), Y = 4X ................(1)
Five years ago:
ratio is 7
7 = (Y-5) / (X-5)
7(X-5) = (Y-5)
7X-35 = Y-5 ........................(2)
(1) in (2)
7X-35 = 4X -5
3X = 30
X = 10 and Y = 40
therefore
Father is 40 years and son is 10 years today.
2006-11-26 7:47 am
let : X = 爸爸
y = 小文
現在----> X = 4y
5年前----> X-5 = (y-5) x7
than X-5 = 7y - 35
X = 7y -30
現在----> X = 4y
Than 4y= 7y -30
3y= 30
y = 10
答現在 爸爸40 小文10
y = 小文
現在----> X = 4y
5年前----> X-5 = (y-5) x7
than X-5 = 7y - 35
X = 7y -30
現在----> X = 4y
Than 4y= 7y -30
3y= 30
y = 10
答現在 爸爸40 小文10
收錄日期: 2021-04-24 08:25:04
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061125000051KK05585