1) 4/21×7/16= (4*7) / (21*16) = 1 / (3*4) = 1/12
2) 3×1_5/9= 3/1 * 14/9 = 14/3 = 4_2/3
3) 4_1/5×2_1/7 =21/5 * 15/7 = (21*15) / (5*7) = (3*3) / 1 = 9/1 = 9
4) 1_7/8×1_1/9 × 1_23/25 =
15/8 * 10/9 * 48/25 = (15*10*48) / (8*9*25) = (1*10*2) / (1*1*5) = 20/5 = 4/1 = 4
5) 8/21 × 1,05 × 1 цел. 2/3 = 4цел.11/20