1.某班共有42名學生參加一次數學測驗。若男生的平均分為49分,女生平均分為63分,而全班的平均分為57分,男,女各有多少人?
2.農場內的豬比雞多20隻。若牠們的腳的總數不少於600隻,那麼最少有多少隻雞?
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2008-08-22 10:11 pm
回答 (1)
2008-08-23 5:54 am
✔ 最佳答案
Q1.Let no. of boy = B, therefore no. of girls = 42 -B.
Total marks of the boys = 49B.
Total marks of the girls = 63(42 - B).
So average mark = [49B + 63(42 - B)]/42 = 57
49B + 2646 - 63B = 2394
14B = 252
B = 18. So there are 18 boys and 24 girls.
Q2.
Let no of chicken = C. So no. of pig = C + 20.
Total no of chicken legs = 2C.
Total no. of pig legs = 4(C + 20).
So 2C + 4(C + 20) > 600
2C + 4C + 80 > 600
6C > 520
C > 86.7
So there are at least 87 chickens.
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