Practice on calculating area

### 1.1. Knowledge to remember

**For example: **Calculate the area of the plot of land with dimensions according to the figure below:

We can do the following:

a) Divide the land into rectangle ABCD and two equal squares EGHK, MNPQ.

b) Calculate the area of the land

The DC side length is:

25 + 20 + 25 = 70 (m)

The area of rectangle ABCD is:

70 x 40.1 = 2807 (m^{2})

The area of two squares EGHK and MNPQ is:

20 x 20 x 2 = 800 (m^{2})

The area of the land is:

2807 + 800 = 3607 (m^{2})

### 1.2. Solve textbook exercises page 104

**Lesson 1 Textbook page 104**

Calculate the area of the plot of land with dimensions according to the figure below.

__Solution guide:__

Divide the given figure into two rectangles, shape I and figure II:

The length of rectangle I is:

3.5 + 4.2 + 3.5 = 11.2 (m)

The area of rectangle I is:

11.2 x 3.5 = 39.2 (m^{2})

The area of rectangle II is:

6.5 x 4.2 = 27.3 (m^{2})

The area of the land is:

39.2 + 27.3 = 66.5 (m^{2})

Answer: 66.5m^{2}

Lesson 2 Textbook page 104

A plot of land has the dimensions as shown in the figure below. Calculate the area of the land plot.

__Solution guide:__

The area of the lot is equal to the area of the covered rectangle minus the area of the two small rectangles with sizes 50m and 40.5m.

The length of the covered rectangle is:

40.5 + 100.5 = 141 (m)

The width of the covering rectangle is:

50 + 30 = 80 (m)

The area of the covered rectangle is:

141 x 80 = 11280 (m^{2})

The sum of the areas of the two small rectangles is:

(50 x 40.5 )x 2 = 4050 (m .)^{2})

The area of the land is:

11280 – 4050 = 7230 (m^{2})

Answer: 7230m^{2}

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