David has types of banknote,$10-notes,$20-notes and $50-notes,in his wallet.The number of $20-notes is fewer than of $10-notes by 5,while the number of $50-notes is more than half of the number of $20-notes by 7.If David has 22 banknotes altogether,find the number of each type of banknote in his wallet.
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f.1英文數學(EASY)
2009-12-27 9:39 pm
回答 (2)
2009-12-27 10:20 pm
✔ 最佳答案
The number of each type of banknote in David's wallet:let n = no. of $20
$10 = n + 5
$50 = n/2+7
22 = n+(n+5)+(n/2+7)
22 = 2n+5+(n/2+7)
22 = 2 + n/2+12
22-12 = 2 + n/2
10 = 5/2n
20 = 5n
20/5 = n
4 = n
There are 4 banknotes of $20
There are 9 banknotes of $10
There are 9 banknotes of $50
參考: me
2009-12-27 10:57 pm
大偉有類型的鈔票， 10元紙幣， 20元和50元紙幣。
20元紙幣少個10元紙幣by 5元.
50元紙幣有多過20元紙幣的一半by 7 元.
如果大偉有22個紙幣, 找他每一個紙幣在他錢包類別的數目.
************************
20元紙幣 就是 x
$10 = x + 5
$50 = x/2+7
...............................
x+(x+5)+(x/2+7)= 22
2x+5+(x/2+7)=22
22 = 2x + x/2+12
22-12 = 2x + x/2
10 = 2x + x/2
.........x2...........
20 = 4x + x
20/5 = 4
x = 4
...........................................
x+5=y
4+5=9
y=9
......................
有4張20元紙幣
有9張10元紙幣
有9張50元紙幣
20元紙幣少個10元紙幣by 5元.
50元紙幣有多過20元紙幣的一半by 7 元.
如果大偉有22個紙幣, 找他每一個紙幣在他錢包類別的數目.
************************
20元紙幣 就是 x
$10 = x + 5
$50 = x/2+7
...............................
x+(x+5)+(x/2+7)= 22
2x+5+(x/2+7)=22
22 = 2x + x/2+12
22-12 = 2x + x/2
10 = 2x + x/2
.........x2...........
20 = 4x + x
20/5 = 4
x = 4
...........................................
x+5=y
4+5=9
y=9
......................
有4張20元紙幣
有9張10元紙幣
有9張50元紙幣
收錄日期: 2021-05-01 01:10:39
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