1. is doing/ does

2. use/ am not using

Chiều rộng: 36 x \(\dfrac{2}{3}\)= 24

Chu vi: (36 + 24) x 2 = 120 (m)

Diện tích: 36 x 24 = 864 (\(^{m^2}\))

ĐS:,.,.,.,.,.,.

y x 2,5 = \(\dfrac{40}{5}:\dfrac{20}{5}\)

y x 2,5 = 2

      y   = 2 : 2,5

      y = 0,8

\(\dfrac{3}{2}m^2\) =  1500 \(cm^2\)

x = 7/3 - 8/9

x = 21/9 - 8/9

x = 13/9

a, X = 8 + 24/8

X = 11

b, X x 17/3 = 76/18 - 4/9

X x 17/3 = 34/9

X = 34/9 : 17/3

X = 2/3

Đặt A = \(\dfrac{3}{6\cdot8}+\dfrac{3}{8\cdot10}+...+\dfrac{3}{158\cdot160}\)

A = \(\dfrac{3}{2}\cdot\left(\dfrac{2}{6\cdot8}+\dfrac{2}{8\cdot10}+...+\dfrac{2}{158\cdot160}\right)\)

A = \(\dfrac{3}{2}\cdot\left(\dfrac{1}{6}-\dfrac{1}{8}+\dfrac{1}{8}-\dfrac{1}{10}+...+\dfrac{1}{158}-\dfrac{1}{160}\right)\)

A = \(\dfrac{3}{2}\cdot\left(\dfrac{1}{6}-\dfrac{1}{160}\right)\)

A = \(\dfrac{3}{2}\cdot\dfrac{77}{480}\)

A = \(\dfrac{77}{320}\)

Vậy: A = \(\dfrac{77}{320}\)

Khối gỗ đó nặng:

        (2,4 x 2,4 x 2,4) x 0,5 = 6,912 (kg)

                  ĐS:.........