3个班捐款,1班捐款是另外2个班捐款数的3分之2,2班捐款是另外2个班的5分之3,3班比2班少72元,共捐多少钱.

问题描述:

3个班捐款,1班捐款是另外2个班捐款数的3分之2,2班捐款是另外2个班的5分之3,3班比2班少72元,共捐多少钱.

1班捐款是另外2个班捐款数的3分之2 占总数(2/3)/(1+2/3)=2/5
2班捐款是另外2个班的5分之3占总数(3/5)(1+3/5)=3/8
3班占总数 1-2/5-3/8=9/40
总数72/(3/8-9/40)=72/(6/40)=480元