Đáp án:
a) $\frac{2}{3}$ ×$\frac{10}{21}$ ×$\frac{3}{2}$
= ( $\frac{2}{3}$ ×$\frac{3}{2}$ )× $\frac{10}{21}$
= 1 × $\frac{10}{21}$ =$\frac{10}{21}$
b) $\frac{22}{5}$ ×12×$\frac{5}{22}$
= ($\frac{22}{5}$ ×$\frac{5}{22}$ )×12
= 1× 12= 12
c) $\frac{7}{2}$ ××$\frac{23}{81}$ ×$\frac{2}{7}$
=($\frac{7}{2}$ ×$\frac{2}{7}$ ) ×$\frac{23}{81}$
=1 ×$\frac{23}{81}$ = $\frac{23}{81}$
d) $\frac{5}{17}$ ×$\frac{21}{4}$ ×$\frac{47}{15}$ ×0= 0
Câu 2:
a) ($\frac{1}{2}$ +$\frac{3}{4}$ )× 4
= $\frac{5}{4}$ ×4= 5
b) ($\frac{5}{7}$ - $\frac{1}{14}$ )×7
= ($\frac{10}{14}$ -$\frac{1}{14}$ )×7
= $\frac{9}{14}$ × 7
= $\frac{9}{2}$
c) $\frac{1}{2}$ ×$\frac{3}{4}$ + $\frac{1}{2}$ ×$\frac{1}{4}$
= $\frac{1}{2}$ ×($\frac{3}{4}$ + $\frac{1}{4}$ )
= $\frac{1}{2}$ × 1= $\frac{1}{2}$
d) $\frac{11}{3}$ ×$\frac{26}{7}$ -$\frac{26}{7}$ ×$\frac{8}{3}$
= $\frac{26}{7}$ ×($\frac{11}{3}$ - $\frac{8}{3}$ )
= $\frac{26}{7 }$ × 1 = $\frac{26}{7}$
Câu 3:
a) $\frac{2}{4}$ ÷$\frac{1}{7}$ = $\frac{2}{4}$ ×$\frac{7}{1}$ = $\frac{7}{2}$
4 ÷ $\frac{2}{3}$ = 4×$\frac{3}{2}$ = 6
3 ÷$\frac{3}{5}$ =3 × $\frac{5}{3}$ = 5
b) $\frac{4}{9}$ ÷2= $\frac{4}{9}$ ×$\frac{1}{2}$ = $\frac{2}{9}$
$\frac{3}{5}$ ÷2= $\frac{3}{5}$ ×$\frac{2}{1}$ = $\frac{3}{10}$
$\frac{10}{21}$ ÷5= $\frac{10}{21}$ ×$\frac{1}{5}$= $\frac{2}{21}$
