a: \(=\left(\dfrac{5}{8}-\dfrac{28}{8}\right)\cdot\dfrac{5}{6}=\dfrac{-23}{8}\cdot\dfrac{5}{6}=\dfrac{-115}{48}\)

b: \(=\dfrac{4}{7}\cdot\dfrac{24+25}{15}=\dfrac{4}{7}\cdot\dfrac{49}{15}=\dfrac{28}{15}\)

c: \(=\dfrac{7}{2}:\dfrac{24-10}{15}=\dfrac{7}{2}\cdot\dfrac{15}{14}=\dfrac{15}{4}\)

Tính bằng cách thuận tiện nhất 3/5 + 3/8 + 2/5 + 5/8 bằng

A.3/7

B.3/5

C.5/7

D.11/2

k hộ mình nha!

\(a,\dfrac{3}{2}\times\dfrac{4}{5}\times\dfrac{2}{3}\times\dfrac{15}{4}\\ =\dfrac{3\times4\times2\times15}{2\times5\times3\times4}\\ =\dfrac{3\times4\times2\times5\times3}{2\times5\times3\times4}\\ =3\)

\(b,\dfrac{6}{7}\times\dfrac{5}{8}\times\dfrac{7}{3}\times\dfrac{7}{6}\times\dfrac{8}{5}\\ =\dfrac{6\times5\times7\times7\times8}{7\times8\times3\times6\times5}\\ =\dfrac{7}{3}\)

a) \(\dfrac{3}{2}\times\dfrac{4}{5}\times\dfrac{2}{3}\times\dfrac{15}{4}\)

\(=\left(\dfrac{3}{2}\times\dfrac{2}{3}\right)\times\left(\dfrac{4}{5}\times\dfrac{15}{4}\right)\)

\(=1\times3\)

\(=3\)

b) \(\dfrac{6}{7}\times\dfrac{5}{8}\times\dfrac{7}{3}\times\dfrac{7}{6}\times\dfrac{8}{5}\)

\(=\left(\dfrac{6}{7}\times\dfrac{7}{6}\right)\times\left(\dfrac{5}{8}\times\dfrac{8}{5}\right)\times\dfrac{7}{3}\)

\(=1\times1\times\dfrac{7}{3}\)

\(=\dfrac{7}{3}\)

Chúc bạn học tốt

a, (6/11+5/11)x3/17

c1:=1x3/17

    =3/17

c2:=6/11x3/17+5/11x3/17

    =18/197+15/187

    =33/187

    =3/17

b,3/5x7/9-3/5x2/9

c1:=21/45-6/45

=15/45

=1/3

c2:=3/5x(7/9-2/9)

=3/5x5/9

=1/3

c,( 6/7-4/7):2/5

c1:=2/7:2/5

=2/7x5/2

=5/7

c2,6/7:2/5-4/7:2/5

=6/7x5/2-4/7x5/2

=15/7-10/7

=5/7

d,8/15:2/11+7/15:2/11

c1:=(8/15+7/15):2/11

=1x11/2

=11/2

c2:=8/15x11/2+7/15x11/2

=88/30+77/30

=165/30

=11/2

a) (\(\frac{6}{11}\) + \(\frac{5}{11}\)) x \(\frac{3}{17}\)=  \(\frac{11}{11}\) x \(\frac{3}{17}\)= \(1\) x\(\frac{3}{17}\)= \(\frac{3}{17}\)

b) \(\frac{3}{5}\)x\(\frac{7}{9}\)- \(\frac{3}{5}\)x \(\frac{2}{9}\) = \(\frac{3}{5}\)x (\(\frac{7}{9}\)- \(\frac{2}{9}\))= \(\frac{3}{5}\) x  \(\frac{5}{9}\)= \(\frac{3}{9}\)

c) (\(\frac{6}{7}\)- \(\frac{4}{7}\)) : \(\frac{2}{5}\)= \(\frac{2}{7}\) x \(\frac{5}{2}\)= \(\frac{5}{7}\)

d) \(\frac{8}{15}\) : \(\frac{2}{11}\) + \(\frac{7}{15}\): \(\frac{2}{11}\)=  ( \(\frac{8}{15}\)+ \(\frac{7}{15}\)) x \(\frac{11}{2}\)= 1 x \(\frac{11}{2}\)= \(\frac{11}{2}\)

Chúc học tốt nha!

a,3/17

b,1/3

c,5/7

d,11/2

chúc bạn hk tốt nhé(nhớ k cho tiu)