\(\dfrac{21}{16}\times\dfrac{8}{5}\times\dfrac{15}{7}=\dfrac{21\times8\times15}{16\times5\times7}=\dfrac{7\times3\times8\times5\times3}{8\times2\times5\times7}=\dfrac{3\times3}{2}=\dfrac{9}{2}\)

\(\dfrac{18}{9}\times\dfrac{9}{36}\times\dfrac{27}{3}=2\times\dfrac{1}{4}\times9=\dfrac{1}{2}\times9=\dfrac{9}{2}\)

a) (25x32) : 8           

= 25 x (4 x 8) : 8

= (25 x 4) x (8:8)

= 100 x 1

=100

b, 24 x 11 + 6 x 86 x 4 + 72

= 24 x 11 + (6 x 4) x 86 + 24 x 3

= 24 x 11 + 24 x 86 + 24 x 3

= 24 x (11+86+3)

= 24 x 100

= 2 400

\(\left(25\times32\right):8=25\times32:8=25\times\left(32:8\right)=25\times4=100\\ 24\times11+6\times86\times4+72\\ =24\times11+24\times86+24\times3\\ =24\times\left(11+86+3\right)\\ =24\times100=2400\\ 36\times5+9\times79\times4+72\times8\\ =36\times5+36\times79+36\times16\\ =36\times\left(5+79+16\right)\\ =36\times100=3600\\ \left(56\times125\right):7=56\times125:7=\left(56:7\right)\times125=8\times125=1000\)

\(a.60\times\left(\frac{7}{12}+\frac{4}{15}\right)\)

\(=60\times\left(\frac{35}{60}+\frac{16}{60}\right)\)

\(=60\times\frac{51}{60}\)

\(=51\)

\(b.\frac{1}{2}\times\frac{2}{3}\times\frac{3}{4}\times\frac{4}{5}\times\frac{5}{6}\times\frac{6}{7}\times\frac{7}{8}\times\frac{8}{9}\)

\(=\frac{1\times2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8\times9}\)

\(=\frac{1}{9}\)

 60x [7/12+4/15]

60x153/180

=9180/180

b 1/2x2/3x3/4x4/5x5/6x6/7x7/8x8/9=40320/4032

giúp mik zứi😭😭😭

a; 60 \(\times\) (\(\dfrac{7}{12}\) + \(\dfrac{4}{15}\)) 

 =  60 \(\times\) \(\dfrac{7}{12}\) + 60 \(\times\) \(\dfrac{4}{15}\)

= 35 + 16

= 51

b; \(\dfrac{1}{2}\) \(\times\)\(\dfrac{2}{3}\) \(\times\) \(\dfrac{3}{4}\) \(\times\) \(\dfrac{4}{5}\) \(\times\) \(\dfrac{5}{6}\) \(\times\) \(\dfrac{7}{8}\) \(\times\) \(\dfrac{8}{9}\)

= \(\dfrac{2\times3\times4\times5\times6\times7\times8}{2\times3\times4\times5\times6\times7\times8}\) \(\times\) \(\dfrac{1}{9}\)

= 1 \(\times\) \(\dfrac{1}{9}\)

= \(\dfrac{1}{9}\)

Bài làm

   \(\frac{7}{15}x\frac{3}{8}+\frac{7}{15}x\frac{5}{8}\)

= \(\frac{7}{15}x\left(\frac{3}{8}+\frac{5}{8}\right)\)

= \(\frac{7}{15}x\frac{8}{8}\)

= \(\frac{7}{15}x1\)

= \(\frac{7}{15}\)

# Chúc bạn học tốt #

\(\frac{7}{15}\cdot\frac{3}{8}+\frac{7}{15}\cdot\frac{5}{8}\)

\(=\frac{7}{15}\cdot(\frac{3}{8}+\frac{5}{8})\)

\(=\frac{7}{15}\cdot1=\frac{7}{15}\)

\(\frac{7}{15}\times\frac{3}{8}+\frac{7}{15}\times\frac{5}{8}\)

\(=\frac{7}{15}\times\left(\frac{3}{8}+\frac{5}{8}\right)\)

\(=\frac{7}{15}\times1\)

\(=\).....................

Tự làm tiếp nhé!

56x24:12=56x2=112

56x24:3x8=56x24:24=56

63x18:9=63x2=126

(36 × 27) : 3 = 36 × (27 : 3)

= 36 × 9

= 324

--------

(125 × 15) : 5

= 125 × (15 : 5)

= 125 × 3

= 375

--------

(15 × 12) : 9

= (5 × 3 × 12) : 9

= 5 × (36 : 9)

= 5 × 4

= 20

--------

450 : (3 × 5)

= 450 : 15

= 30

--------

(45 × 63) : 9

= 45 × (63 : 9)

= 45 × 7

= 40 × 7 + 5 × 7

= 280 + 35

= 315

a: \(\dfrac{\left(36\cdot27\right)}{3}=36\cdot\dfrac{27}{3}=36\cdot9=324\)

b: \(\dfrac{\left(125\cdot15\right)}{5}=125\cdot\dfrac{15}{5}=125\cdot3=375\)

c: \(\dfrac{\left(15\cdot12\right)}{9}=\dfrac{3\cdot3\cdot4\cdot5}{9}=4\cdot5=20\)

d: \(\dfrac{450}{3\cdot5}=\dfrac{450}{15}=30\)

e: \(\dfrac{45\cdot63}{9}=\dfrac{45}{9}\cdot63=63\cdot5=315\)