Question

[hao tranthi]

bài 1 : tính bằng 2 cách

[6/11 + 7/5] x 3/7

[6/7 - 1/2] x 2/5

Answer 1

[subjects]

cách 1 \(\left(\dfrac{6}{11}+\dfrac{7}{5}\right)\cdot\dfrac{3}{7}\\ =\dfrac{107}{55}\cdot\dfrac{3}{7}=\dfrac{321}{385}\)cách 2 \(\left(\dfrac{6}{11}+\dfrac{7}{5}\right)\cdot\dfrac{3}{7}\\ =\dfrac{6}{11}\cdot\dfrac{3}{7}+\dfrac{7}{5}\cdot\dfrac{3}{7}\\ =\dfrac{18}{77}+\dfrac{3}{5}=\dfrac{321}{385}\)

cách 1 \(\left(\dfrac{6}{7}-\dfrac{1}{2}\right)\cdot\dfrac{2}{5}\\ =\dfrac{5}{14}\cdot\dfrac{2}{5}=\dfrac{1}{7}\) cách 2 \(\left(\dfrac{6}{7}-\dfrac{1}{2}\right)\cdot\dfrac{2}{5}\\ =\dfrac{6}{7}\cdot\dfrac{2}{5}-\dfrac{1}{2}\cdot\dfrac{2}{5}\\ =\dfrac{12}{35}-\dfrac{1}{5}=\dfrac{1}{7}\)

Answer 2

[Nguyễn Thị Thương Hoài]

[ \(\dfrac{6}{11}\)  + \(\dfrac{7}{5}\)] x \(\dfrac{3}{7}\)

= [ \(\dfrac{30}{55}\) + \(\dfrac{77}{55}\)] x \(\dfrac{3}{7}\)

= \(\dfrac{107}{55}\)x \(\dfrac{3}{7}\)

= \(\dfrac{321}{385}\)

[ \(\dfrac{6}{11}\) + \(\dfrac{7}{5}\)] x \(\dfrac{3}{7}\)

= \(\dfrac{6}{11}\) x \(\dfrac{3}{7}\) + \(\dfrac{7}{5}\) x \(\dfrac{3}{7}\)

= \(\dfrac{18}{77}\)   +  \(\dfrac{3}{5}\)

= \(\dfrac{90}{385}\) + \(\dfrac{231}{385}\)

= \(\dfrac{321}{385}\)

 [ \(\dfrac{6}{7}\) - \(\dfrac{1}{2}\)] x \(\dfrac{2}{5}\)

= [ \(\dfrac{12}{14}\) - \(\dfrac{7}{14}\)] x \(\dfrac{2}{5}\)

= \(\dfrac{5}{14}\)  x \(\dfrac{2}{5}\)

= \(\dfrac{1}{7}\)

[ \(\dfrac{6}{7}\) - \(\dfrac{1}{2}\)] x \(\dfrac{2}{5}\)

= \(\dfrac{6}{7}\) x \(\dfrac{2}{5}\) - \(\dfrac{1}{2}\) x \(\dfrac{2}{5}\)

= \(\dfrac{12}{35}\) - \(\dfrac{1}{5}\)

= \(\dfrac{12}{35}\) - \(\dfrac{7}{35}\)

= \(\dfrac{5}{35}\)

= \(\dfrac{1}{7}\)