B1: tính `a)4x7/9` `b)5/7x6` `c)3/5x7` `d)11/4x4` b2:Tính rồi rút gọn(giải thích rõ) `a)3/5x4/7` `b)2/9x5/6` `c)9/14x7/3` `d)11/6x4/22

Bài 1 : Tính 
$\text{a)  4 $\times$}$ $\dfrac{7}{9}$ = $\dfrac{4 \times 7}{9}$ = $\dfrac{28}{9}$

$\text{b)}$ $\dfrac{5}{7}$ $\text{$\times$ 6}$ = $\dfrac{5 \times 6}{7}$ = $\dfrac{30}{7}$

$\text{c)}$ $\dfrac{3}{5}$ $\text{$\times$ 7}$ = $\dfrac{3 \times 7}{5}$ = $\dfrac{21}{5}$

$\text{d)}$ $\dfrac{11}{4}$ $\text{$\times$ 4}$ = $\dfrac{11 \times 4}{4}$ = $\dfrac{44}{4}$ = $\text{11}$

Bài 2 : Tính rồi rút gọn ( giải thích rõ )
$\text{a)}$ $\dfrac{3}{5}$ $\times$ $\dfrac{4}{7}$ = $\dfrac{3 \times 4}{5 \times 7}$ = $\dfrac{12}{35}$

$\text{b)}$ $\dfrac{2}{9}$ $\times$ $\dfrac{5}{6}$ = $\dfrac{2 \times 5}{9 \times 6}$ = $\dfrac{10}{54}$ = $\dfrac{10 : 2}{54 : 2}$ = $\dfrac{5}{27}$

$\text{c)}$ $\dfrac{9}{14}$ $\times$ $\dfrac{7}{3}$ = $\dfrac{9 \times 7}{14 \times 3}$ = $\dfrac{63}{42}$ = $\dfrac{63 : 21}{42 : 21}$ = $\dfrac{3}{2}$

$\text{d)}$ $\dfrac{11}{6}$ $\times$ $\dfrac{4}{22}$ = $\dfrac{11 \times 4}{6 \times 22}$ = $\dfrac{44}{132}$ = $\dfrac{44 : 44}{132 : 44}$ = $\dfrac{1}{3}$

#YN_Yuri

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