设原一班有x人,原二班有y人.
(1-1/3-1/4)x+(1-1/3-1/4)y=30 x+y=72
x/3+y/4=(x/4+y/3)*(1+10%) x=2y
2y+y=72 3y=72 y=24
x=2*24=48
答:原一班有48人.