Review on calculating area and volume of some shapes

### 1.1. Knowledge to remember

\(\begin{array}{l}

{S_{xq}} = \left( {a \times b} \right) \times 2 \times c\\

{S_{tp}} = {S_{xq}} + {S_{day}} \times 2\\

V = a \times b \times c

\end{array}\)

\(\begin{array}{l}

{S_{xq}} = a \times a \times 4\\

{S_{tp}} = a \times a \times 6\\

V = a \times a \times a

\end{array}\)

### 1.2. Solve textbook exercises page 168

**Lesson 1 Textbook page 168**

A classroom has the shape of a rectangular box with a length of 6m, a width of 4.5m and a height of 4m. They wanted to whitewash the ceiling and the four walls inside the room. Knowing that the area of the doors is 8.5m^{2}, calculate the area to be whitewashed.

__Solution guide:__

The ceiling area is:

6 x 4.5 = 27 (m^{2})

The area around the classroom is:

(6 + 4.5) x 2 x 4 = 84 (m^{2})

The area to be whitewashed is:

27 + 84 – 8.5 = 102.5 (m^{2})

Answer: 102.5m^{2}.

Lesson 2 Textbook page 168

An’s friend makes a cube-shaped box out of cardboard with a side of 10cm.

a) Calculate the volume of that box.

b) If all sides of the box are glued with colored paper, how many square centimeters of colored paper will An need to use?

__Solution guide:__

a) The volume of the cube is:

10 x 10 x 10 = 1000 (cm^{3})

b) The area of colored paper needed to glue all the outside faces of the box is the total area of the cube.

The required area of colored paper is:

10 x 10 x 6 = 600 (cm^{2})

Answer: a) 1000cm^{3};

b) 600cm^{2}

Lesson 3 Textbook page 168

A rectangular water tank has dimensions in the tank: length 2m, width 1.5m and height 1m. When the tank has no water, people open the faucet to let water flow into the tank, each hour is 0.5m3. After how many hours will the tank be full?

__Solution guide:__

The volume of the water tank is:

2 x 1.5 x 1 = 3 (m^{3})

The tank will be full after the number of hours is:

3: 0.5 = 6 (hours)

Answer: 6 hours.

.

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