长江中学对七年级的男生进行跳绳测试,规定100个达标,超过的次数用正数表示,不足的次数用负数表示,其中10名男生的测试结

解题思路：先分别求出各班的总成绩，再把各班的总成绩加起来除以八年级4个班的人数，即可得出答案．

根据题意得：
（81×55+90×40+85×45+84×60）÷（55+40+45+60）
=16920÷200
=84.6（分）．
答：本次考试八年级（共4个班）的数学平均分是84.6分．

点评：
本题考点： 加权平均数．

考点点评： 本题考查的是加权平均数的求法，掌握加权平均数的计算公式是本题的关键．

We often give money to the people in poor or disaster-stricken areas. Some students don’t think it a good way to help people there .However ,some prefer helping the unfortunate with money.
In their opinion, money can be used to buy daily necessities and can help people rebuild their hometowns ,while sometimes the things people there receive are not what they need actually.
But some other students think that giving used clothing to the people in those areas is better .Many people ,especially in rich areas and in cities ,have much clothing they no longer like or need. By giving it away to the needy people we can make the best use of it . Besides ,we are just students ,and we have no incomes of our own.
Anyhow ,no matter which way is considered better ,we should try our best to help those who need help.

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