Question

Tính bằng 2 cách: a/ \(4\frac{3}{7}.2\)                              b/ \(5\frac{1}{2}.3\)

Answer 1

a, C1:   \(4\frac{3}{7}.2=\frac{31}{7}.2=\frac{31.2}{7}=\frac{62}{7}=8\frac{6}{7}\)

   C2:   \(4\frac{3}{7}.2=\left(4+\frac{3}{7}\right).2=\left(4.2\right)+\left(\frac{3}{7}.2\right)=8+\frac{6}{7}=8\frac{6}{7}\)

b, C1:  \(\frac{11}{2}.3=\frac{11.3}{2}=\frac{33}{2}=16\frac{1}{2}\)

   C2:   \(5\frac{1}{2}.3=\left(5+\frac{1}{2}\right).3=\left(5.3\right)+\left(\frac{1}{2}.3\right)=15+1\frac{1}{2}=16\frac{1}{2}\)