TOMORROW NEED TO HAND IN!! PLZ HELP!!

[匿名]

2008-01-02 7:04 am

David has three types of banknotes,$10-note,$20-note and $50-note, in his wallet. The number of$20-note is less than that $ 10-note by 5, while the number of$50-note is more than half of the number of $20-note by 7. If David has22 banknotes altogether, find the number of each type of banknotes in his wallet.
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回答 (1)

STEVIE-G™

2008-01-02 7:14 am

✔ 最佳答案

Let the number of $10-note number be x
then the number of $20-note number be (x-5)
and the number of $50-note number be [(x-5)/2+7]
David has22 banknotes altogether
the number of $10-note number +the number of $20-note number +the number of $50-note number =22
x+(x-5)+ [(x-5)/2+7]=22
multiply both sides by 2,
2x+2(x-5)+(x-5)+14=44
2x+2x-10+x-5=44-14
5x=30+10+5
5x=45
x=9
Therefore,
the number of $10-note number is 9
then the number of $20-note number is (9-5)=4
and the number of $50-note number is [(9-5)/2+7]=9

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