Question

某校去年570人,今年610人,今年男生增加去年的1/6,女生减少去年的1/5,去年男生比女生多多少人.

Answer 1

设女生原来有x人,则男生原来有570-x人.

4/5x+(570-x)*6/7=610

5/4x+570*6/7-6/7x=610

5/4x+665-6/7x=610

665-(6/7x-5/4x)=610

665-(30/35x-30/11x)=610

665-30/11x=610

665-610=30/11x

55=33/11x

x=55*11/30

x=150

570-x=570-150=420

420-150=270

答：多270人.