Cách 1:

\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\)

\(=\frac{8}{15}\times\frac{5}{6}\)

\(=\frac{4}{9}\)

Cách 2:

\(\left(\frac{2}{3}\times\frac{4}{5}\right)\times\frac{5}{6}\)

\(=\frac{2}{3}\times\left(\frac{4}{5}\times\frac{5}{6}\right)\)

\(=\frac{2}{3}\times\frac{2}{3}\)

\(=\frac{4}{9}\)

= 2/7+5/7+1/5+4/5

=7/7+5/5

=1+1

=2

( 2/7 + 5/7 ) + ( 1/5 + 4/5 )

= 1 + 1

= 2

= (2/7+5/7)+(1/5+4/5)

=1+1=2

Lớp 8 đâu?

lp 6 đâu

lớp 6 đâu

Đặt \(\frac{x_1-1}{5}=\frac{x_2-2}{4}=\frac{x_3-3}{3}=\frac{x_4-4}{2}=\frac{x_5-5}{1}=k\)

Áp dụng TC DTSBN ta có :

\(k=\frac{\left(x_1-1\right)+\left(x_2-2\right)+\left(x_3-3\right)+\left(x_4-4\right)+\left(x_5-5\right)}{5+4+3+2+1}\)

\(=\frac{x_1+x_2+x_3+x_4+x_5-15}{15}=\frac{30-15}{15}=1\)

\(\frac{x_1-1}{5}=1\Rightarrow x_1=6;\frac{x_2-2}{4}=1\Rightarrow x_2=6;\frac{x_3-3}{3}=1\Rightarrow x_3=6;\frac{x_4-4}{2}=1\Rightarrow x_4=6;\frac{x^5-5}{2}=1\Rightarrow x_5=6\)

Vậy \(x_1=x_2=x_3=x_4=x_5=6\)

a) 24/35

b) 2/5

c) 1/6

d) 1/7

a) 24/35
b) 2/5
c) 1/6
d) 1/7

a)cách 1

=8/15 x 1/2

=8/30

cách 2 

=1/3 x 1/2 + 1/5 x 1/2

=1/6 + 1/10

=8/30

b) cách 1

=2/.15 x 1/2

=2/30

cách 2

=1/3 x 1/2 - 1/5 x 1/2

=1/6 - 1/10

=2/30

nhớ tk nha

nhớ tk nha