a) 2,52 × 3,2 = 8.064 = 8064 /1000 = 4032/ 500= 2016 / 250 = 1008/ 125
b) 5/ 7 × 2,8 = 5/7 × 28 /10 = ( 5·28) / ( 7 ·10) = 140 / 70 = 14/ 7 = 2
c) 9 / 38 × 4,(2) = 9 /38 × 4 intregi 2/9 = 9 /38 × ( 4·9 + 2) / 9
= 9 /38 × 38 /9 = ( 9· 38) / ( 38 · 9) , se simplifica = 1