数学题:调查发现，该学校七年级参加魔方比赛的学生中，男生人数是女生的2倍，男生、女生获奖人数分别为70人和45人，女生获奖率比男生高12.5%，求七年级参加魔方比赛总人数。

数学题解答：设女生为x人。求出x后，再算男生人数，最后求出总人数。

45÷x – 70÷(2x)=12.5%

方程两边同时乘x，得：

12.5%x = 45-35

x = 80

男生人数：80×2=160（人）

总人数：80+160=240（人）

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