有math唔識...高手快入睇睇,要做功課(解方程式問題)
2006-10-23 2:36 am
(解方程式問題)1個人買左一些$2同一些$5既郵票.如果佢一次用$54買左15張郵票,問佢買左幾多張$2既郵票?....我知個佢係買左7張$2既郵票...但係我唔識條式.....要做功課...thx
回答 (2)
2006-10-23 2:52 am
✔ 最佳答案
設$2郵票是x張2x+5(15-x)=54
2x+75-5x=54
2x-5x=54-75
-3x=-21
x=7
參考: MYSELF
2006-10-23 2:44 am
let x為$2郵票數量 ; y為$5郵票數量
2(x) + 5(y) = 54 ...[1]
x + y = 15 ...[2]
from [2]
x+y=15
x=15-y ...[3]
put [3] into [1]
2(15-y) + 5(y) = 54
30 - 2y + 5y = 54
3y = 24
y=8
put [y=8] into [3]
x=15-8
x=7
2(x) + 5(y) = 54 ...[1]
x + y = 15 ...[2]
from [2]
x+y=15
x=15-y ...[3]
put [3] into [1]
2(15-y) + 5(y) = 54
30 - 2y + 5y = 54
3y = 24
y=8
put [y=8] into [3]
x=15-8
x=7
收錄日期: 2021-04-13 14:17:45
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20061022000051KK04474