Cách 1: (27 × 108) : 9 = 2916 : 9 = 324

Cách 2: (27 × 108) : 9 = (27 : 9) × 108 = 3 × 108 = 324

Cách 1:

(27*108):9

=2916:9

=324

Cách 2:

(27*108):9

=(27:9)*108

=3*108

=324

cách 1: 20 + 3 = 23

cách 2: 20 + (3\(^3\): 3\(^2\)) = 20 + 3 = 23

cách 3: 20 + (9.3 : 9) = 20 + 3 = 23

\(\dfrac{2}{1\times3}+\dfrac{2}{3\times5}+\dfrac{2}{5\times7}+...+\dfrac{2}{13\times15}+\dfrac{2}{15\times17}\)

\(=1-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{13}-\dfrac{1}{15}+\dfrac{1}{15}-\dfrac{1}{17}\)

\(=1-\dfrac{1}{17}\)

\(=\dfrac{16}{17}\)

\(\dfrac{2}{1\cdot3}+\dfrac{2}{3\cdot5}+...+\dfrac{2}{15\cdot17}\)

\(=2-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{7}+...+\dfrac{1}{15}-\dfrac{1}{17}\)

\(=2-\dfrac{1}{17}\)

\(=\dfrac{33}{17}\)

\(=13\cdot70\cdot\left(\frac{1}{7}+\frac{1}{10}\right)=13\cdot\left(\frac{70}{7}+\frac{70}{10}\right)=13\cdot\left(10+7\right)=13\cdot17=221.\)

Vậy....

=70x13/7+70x13/10

=10x13+7x13

=130+91

=221

11 12 13 14 nha mình mới nghĩ đó

Bn than khảo link này nha :

https://olm.vn/hoi-dap/detail/39223661163.html

~ Hok tốt ~

TL:

Chiều rộng thửa ruộng là:

         \(120x\frac{2}{3}\)\(=80\left(m\right)\)

Diện tích thửa ruộng là:

           \(120x80=9600\left(m^2\right)\)

Diện tích trồng cây ăn quả là:

             \(9600x\frac{2}{3}\)\(=6400\left(m^2\right)\)

Diện tích Trồng hoa là:

              \(9600-6400=3200\left(m^2\right)\)

                                   Đ/S: 3200 m²

~HT~

1.

\(a,\frac{1}{7}+\frac{3}{4}+\frac{2}{7}+\frac{4}{7}=\frac{1}{7}+\frac{2}{7}+\frac{4}{7}+\frac{3}{4}\)

\(=1+\frac{3}{4}=\frac{7}{4}.\)

\(b,\frac{4}{7}:\frac{2}{5}+\frac{3}{7}:\frac{2}{5}-\frac{7}{9}=\left(\frac{4}{7}+\frac{3}{7}\right):\frac{2}{5}-\frac{7}{9}\)

\(=1:\frac{2}{5}-\frac{7}{9}=\frac{5}{2}-\frac{7}{9}\)

\(=\frac{31}{18}.\)

a)3/4+(1/7+2/7+4/7)

=3/4+1

=7/4

b)2/5:(4/7+3/7)-7/9

=2/5:1-7/9

=2/5-7/9

=-17/45

31/18