小明为美术兴趣小组买回80枝画笔,有2元一枝,5元一枝,10元一枝的,共付490元,己知5元一枝和10元一枝的笔的数量相同.求出三种画笔各有多少枝?(列式计算)
人气:255 ℃ 时间:2020-02-03 05:54:37
解答
5元和10元的:(490-80X2)÷[(5-2)+(10-2)]
=(490-160)÷[3+8]
=330÷11
=30
2元的:80-30-30=20
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