有红黄两种颜色的小球共140个

  • 时间:2020-05-31 15:09:42
  • 分类:数学世界
  • 阅读:176 次

有红黄两种颜色的小球共140个,拿出红球的1/4,再拿出7个黄球,剩下的红球和黄球正好-样多。原来红球和黄球各有多少个?

数学题解答:题中有红黄两种小球,且告诉了它们的总数,要求两种小球各有多少个。另外,题中还有“剩下的红球与黄球一样多”的等量关系,所以用方程解答比较容易。

解:设黄球有x个,则红球有(140-x)个。

红球拿起了1/4,还剩下3/4,所以剩下的红球可表示为:(140-x)×(1-1/4),剩下的黄球可表示为x-7,它们是相等的关系。列方程为:

(140-x)×(1-1/4)=x-7

(140-x)×3/4        =x-7

                140×3/4  -3/4x=x-7

                                 7/4 x-7=105

                                       7/4x=105+7

                                      7/4x=112

                                               x=64

黄球有64个,红球有:140-64=76(个)。

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