IXL - Area and perimeter of similar figures (Geometry practice)

The figures below are similar. The labeled sides are corresponding.

6 yd

5 yd

P1 = 18 yd

P2 = ?

What is the perimeter of the smaller triangle?

P2 = yards

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Learn with an example

question

The figures below are similar. The labeled sides are corresponding.

4 m

7 m

A1 = 16 m2

A2 = ?

What is the area of the larger triangle?

A2 = square meters

key idea

The following proportion applies to similar shapes:

where
a
b
is
the
ratio
of
the
corresponding
side
lengths,
and
A1
A2
is
the
ratio
of
the
areas.

solution

Find the square of the ratio of the corresponding side lengths.

Find the ratio of the areas.

Use these two ratios to set up a proportion and solve for A2.

Multiply both sides by 49A2

(

)

(

)

Multiply both sides by 49A2

Simplify

16A2

16 · 49

Simplify

16A2

784

Simplify

Divide both sides by 16

16A2 ÷ 16

784 ÷ 16

Divide both sides by 16

The area of the larger triangle is 49 square meters.

Looking for more? Try these:

Lesson: Similarity

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Not feeling ready yet? These can help:

M.6Perimeters of similar figures

M.14Areas of similar figures

Lesson: Similarity

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