Doi : 42 % = 42/100 = 21/50
Hieu so phan bang nhau la :
50 - 21 = 29 ( phan )
Co so cong nhan nu la :
290 : 29 * 21 = 210 ( cong nhan )
Co so cong nhan nam la :
290 + 210 = 500 ( cong nhan )
Nha may do co so cong nhan la :
210 +500 = 710 ( cong nhan )
D/S : 710 cong nhan