設(shè),現(xiàn)在男生有X人,則原來(lái)男生有X+3人
原來(lái)男生占55%,則總數(shù)是 (X+3)/55%,即原來(lái)女生是[(X+3)/55%]*45%
則現(xiàn)在女生是 [(X+3)/55%]*45%+3
走3個(gè)男生,來(lái)3個(gè)女生,總?cè)藬?shù)不變,那么女生數(shù)為 [(X+3)/55%]*48%
[(X+3)/55%]*45%+3 = [(X+3)/55%]*48%
[(X+3)/55%]*3% = 3
[(X+3)/55%] = 100
(X+3) = 55
X = 52
現(xiàn)在有男生52人.