MAths
2008-08-23 4:40 pm
1.Last month,there were 30 male students and 20 female students in the chess class.The number of male students decreases by r% and the number of female students increases by r% in this month.If the number of male and female students are the same in this month,find r.
回答 (1)
2008-08-23 4:57 pm
✔ 最佳答案
In this month:
No. of male students = 30 x (100 - r)%
No. of female students = 20 x (100 + r)%
30 x (100 - r)% = 20 x (100 + r)%
3 x (100 - r) = 2 x (100 + r)
300 - 3r = 200 + 2r
5r = 100
r = 20
=
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