a: Cách 1: \(\left(\frac58-\frac72\right):\frac65\)

\(=\left(\frac58-\frac{28}{8}\right):\frac65\)

\(=-\frac{23}{8}\cdot\frac56=\frac{-115}{48}\)

Cách 2: \(\left(\frac58-\frac72\right):\frac65\)

\(=\left(\frac58-\frac72\right)\cdot\frac56\)

\(=\frac58\cdot\frac56-\frac72\cdot\frac56\)

\(=\frac{25}{48}-\frac{35}{12}\)
\(=\frac{25}{48}-\frac{140}{48}=\frac{-115}{48}\)

b: Cách 1: \(\frac47\left(\frac85+\frac53\right)\)

\(=\frac47\cdot\frac85+\frac47\cdot\frac53\)

\(=\frac{32}{35}+\frac{20}{21}\)

\(=\frac{96}{105}+\frac{100}{105}=\frac{196}{105}=\frac{28}{15}\)

Cách 2: \(\frac47\left(\frac85+\frac53\right)\)

\(=\frac47\left(\frac{24}{15}+\frac{25}{15}\right)\)

\(=\frac47\cdot\frac{49}{15}\)

\(=\frac{49}{7}\cdot\frac{4}{15}=7\cdot\frac{4}{15}=\frac{28}{15}\)

c: Cách 1: \(\frac72:\left(\frac85-\frac23\right)\)

\(=\frac72:\left(\frac{24}{15}-\frac{10}{15}\right)\)

\(=\frac72:\frac{14}{15}=\frac72\cdot\frac{15}{14}=\frac{15}{2\cdot2}=\frac{15}{4}\)

Tàu là trùm

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

a: \(\frac23+\left(\frac57+\frac{-2}{3}\right)\)

\(=\frac23+\frac57-\frac23\)

\(=\frac57\)

b: \(\left(-\frac14+\frac58\right)+\frac{-3}{8}\)

\(=\frac{-2}{8}+\frac58+\frac{-3}{8}\)

=0

c: \(\frac75\cdot\frac{8}{19}+\frac75\cdot\frac{12}{19}-\frac75\cdot\frac{1}{19}\)

\(=\frac75\left(\frac{8}{19}+\frac{12}{19}-\frac{1}{19}\right)\)

\(=\frac75\cdot\frac{19}{19}=\frac75\)

d: \(6\frac{3}{10}-\left(3\frac47+2\frac{3}{10}\right)\)

\(=6+\frac{3}{10}-3-\frac47-2-\frac{3}{10}\)

\(=1-\frac47=\frac77-\frac47=\frac37\)

e: \(\left(31,12-5,97\right)-\left(-68,88+4,03\right)\)

=31,12-5,97+68,88-4,03

=100-10

=90

f: \(3,7\cdot\left(-10,56\right)+3,7\cdot110,56\)

\(=3,7\cdot\left(-10,56+110,56\right)\)

\(=3,7\cdot100=370\)

A.3/7

B.3/5

C.5/7

D.11/2

k hộ mình nha!

3228

3228 nhé em

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

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

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