simultaneous linear equations

👨🏻‍🏫 學術台數學

[匿名]

2008-10-25 6:16 am

1. David has 10 coins, some of them are $5-coins and the rest are $2-coins.The coins amount to $32 altogether, how many coins of each kind does David have?(set up two equations)
請大家詳細列出怎樣做，plz

更新1:

還有一題 Alan is 24 years younger than his father. Four year ago, his age was one third his father's. Find their present ages. (Set up two equations)

回答 (1)

用戶5569

2008-10-25 7:46 am

✔ 最佳答案

Let x and y be the number of $5-coins and $2-coins respectively.

x+y = 10--------------(1)

5x+2y = 32------------(2)

From(1),

x+y = 10

x = 10-y ---------------(3)

Substitute (3) into (2) ,

5(10-y)+2y = 32

50-5y+2y = 32

3y = 18

y = 6

From (3),

x = 10-(6) = 4

Therefore , David have four $5-coins and six $2-coins.

參考: me(f.4)

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