F.2 Maths
2014-12-28 2:15 am
Ann has seventeen $2 coins and eighteen $5 coins. Ann spent some moneyon lunch. Then, she finds there are twenty- eight coins left with the totalvalue of $101. How many $2 coins does she spend on lunch?
回答 (1)
2014-12-28 2:36 am
✔ 最佳答案
The money she spent:[17(2)+18(5)] - 101
=23
The coins she left:
(17+18)-28
=7
Let the $2 coins and $5 coins that she spent be x and y respectively.
2x+5y=23 ------ (1)
x+y=7 ------ (2)
By transforming (2),
x=7-y ------(2*)
Sub. (2*) into (1),
2(7-y)+5y=23
14+3y=23
3y=9
y=3
Put y=3 into (2),
x+(3)=7
x=4
∴The $2 coins she spent is 4.
參考: ME
收錄日期: 2021-04-15 17:45:36
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https://hk.answers.yahoo.com/question/index?qid=20141227000051KK00087