AREA AND PERIMETER OF SIMILAR FIGURES WORKSHEET

About "Area and perimeter of similar figures worksheet"

Area and perimeter of similar figures worksheet :

Here we are going to see some practice problems based on the concept area and perimeter of the similar figures.

Question 1 :

Find the missing length of following similar shapes

Question 2 :

Find the missing length of following similar shapes

Question 3 :

The perimeters of two similar triangles is in the ratio 3 : 4. The sum of their areas is 75 cm². Find the area of each triangle.

Question 4 :

The areas of two similar triangles are 45 cm² and 80 cm². The sum of their perimeters is 35 cm. Find the perimeter of each triangle.

Area and perimeter of similar figures worksheet - Solution

Two figures that have the same shape are said to be similar. When two figures are similar, the ratios of the lengths of their corresponding sides are equal. To determine if the triangles below are similar, compare their corresponding sides.

length of side AB/length of side AD = Length of side EF/Length of side EH

(4/2) = (8/4)

2 : 1 = 2 : 1

Perimeter :

If two similar triangles have a scale factor of a : b, then the ratio of their perimeters is a : b.

Area :

If two similar triangles have a scale factor of a : b, then the ratio of their areas is a² : b².

Let us see some examples based on the above concept.

Question 1 :

Find the missing length of following similar shapes

Solution :

Since the above rectangles ABCD and EFGH are similar, the ratio of the corresponding sides will be in the same ratio.

Length of side AB/Length of side AD = Length of EF/Length of EH

4/6 = a/12

4 (12) = 6a

a = 48/6

a = 8

Hence the missing length of the rectangle EFGH is 8 cm.

Question 2 :

Find the missing length of following similar shapes

Solution :

Since the above rectangles ABCD and EFGH are similar, the ratio of the corresponding sides will be in the same ratio.

Length of side AB/Length of side AD = Length of EF/Length of EH

b/1 = 7.5/3

b (3) = 7.5 (1)

b = 7.5/3

b = 2.5

Hence the missing length of the rectangle EFGH is 2.5 cm.

Question 3 :

The perimeters of two similar triangles is in the ratio 3 : 4. The sum of their areas is 75 cm². Find the area of each triangle.

Solution :

Since the perimeters of two similar triangles is in the ratio 3 : 4,

Let "3x" be the side length of first triangle

Let "4x" be the side length of second triangle

Area of 1st triangle/Area of 2nd triangle = (3x/4x)²

= 9x²/16x²

The sum of their areas = 75 cm²

9x²+ 16x² = 75

25x² = 75

x² = 75/25 = 3

Area of first triangle = 9x² = 3(3) = 9 cm²

Area of second triangle = 16x² = 16(3) = 48 cm²

Example 4 :

The areas of two similar triangles are 45 cm² and 80 cm². The sum of their perimeters is 35 cm. Find the perimeter of each triangle.

Solution :

let the scale factor of the two similar triangles be a : b.

Area of 1st triangle/Area of 2nd triangle = 45/80

a : b is the reduced form of the scale factor. 3 : 4 is then the reduced form of the comparison of the perimeters.

(9/16) = (a/b)²

(a/b) = 3/4

Perimeter of 1st triangle = 3x

Perimeter of 2nd triangle = 4x

Sum of the perimeters of the 1st and 2nd triangle = 35

3x + 4x = 35

7x = 35 ==> x = 5

Perimeter of 1st triangle = 3x = 3(5) = 15 cm

Perimeter of 2nd triangle = 4x = 4(5) = 20 cm

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