In an enrichment class,1/3 are boys and the restare girls.After 3_数学解答

In an enrichment class,1/3 are boys and the restare girls.After 3 girls and 3 boys leave the class,there are now 2/5 as many boys as girls.How many pupils are there in the class in the end?

人气：427 ℃　时间：2020-01-31 21:00:48

解答

在一个班级里,三分之一是男生,剩下的都是女生.3个男生和3个女生离开班级以后,现在男生人数是女生的五分之二.最后班里还有多少小学生?
21人.
设原来男生有x人,则原来女生有2x人.
x-3/2x-3=2/5
解得x=9
则现在班里有9×3-6=21（人）.