Question

[Nguyễn Thùy Linh]

tính bằng cách thuận tiện:

a, 3/4 + 2/5 + 3/12                                       b, 47/15 +40/17 - 4/30 - 6/17

Answer 1

[Akai Haruma]

Lời giải:

a. $\frac{3}{4}+\frac{2}{5}+\frac{3}{12}=\frac{3}{4}+\frac{2}{5}+\frac{1}{4}$

$=(\frac{3}{4}+\frac{1}{4})+\frac{2}{5}=1+\frac{2}{5}=\frac{7}{5}$

b. $\frac{47}{15}+\frac{40}{17}-\frac{4}{30}-\frac{6}{17}$
$=(\frac{47}{15}-\frac{4}{30})+(\frac{40}{17}-\frac{6}{17})$

$=(\frac{47}{15}-\frac{2}{15})+\frac{34}{17}$

$=\frac{45}{15}+\frac{34}{17}=3+2=5$