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## McGraw-Hill Math Grade 3 Chapter 12 Test Answer Key

**Count or multiply to find the area of each figure.**

Question 1.

Answer:

6 square units

Explanation:

I counted by 1’s

There are 6 squares in the above figure

So, the area of the given figure is 6 square units.

Question 2.

Answer:

4 square units

Explanation:

There are 3 squares and 2 triangles which is 1 square

So, the area of the figure is 4 square units.

Question 3.

Answer:

6 square units

Explanation:

I counted by 1’s

There are 6 squares in the above shape

So, the area of the given figure is 6 square units.

Question 4.

Answer:

12 square units

Explanation:

The multiplication sentence that tells the area of the above figure is 2 x 6 = 12

So, the area of the given figure is 12 square units.

Question 5.

Answer:

11 square units

Explanation:

I counted by 1’s

There are 11 squares in the above shape

So, the area of the given figure is 11 square units.

Question 6.

Answer:

22 square units

Explanation:

I counted by 1’s

There are 22 squares in the above shape

So, the area of the given figure is 22 square units.

**Write a multiplication sentence for each area model.**

Question 7.

Answer:

1 x 3 = 3

Explanation:

There is 1 row and 3 columns of squares

The multiplication sentence for the given area model is 1 x 3 = 3.

Question 8.

Answer:

5 x 5 = 25

Explanation:

There is 5 rows and 5 columns of squares

The multiplication sentence for the given area model is 5 x 5 = 25.

Question 9.

Answer:

2 x 7 = 14

Explanation:

There is 2 rows and 7 columns of squares

The multiplication sentence for the given area model is 2 x 7 = 14.

**Look at the area model. Circle the multiplication sentence that matches.**

Question 10.

4 Ã— (4 + 2) = 16 square units

2 Ã— (4 + 2) = 16 square units

4 Ã— (2 + 2) = 16 square units

Answer:

Explanation:

There are 4 rows of squares

In that 2 columns are brown and 2 columns are yellow

So, the the multiplication sentence that matches with the area model is 4 x (2 + 2) = 16 square units.

Question 11.

Selma is decorating the cover of her journal with stickers. The cover is 6 units by 7 units. Each sticker covers 1 square unit. How many stickers does Selma need to decorate every unit of the whole journal cover? Find 6 Ã— 7 by breaking apart 7. Use 3 for one of the addends. Use the area model to help you.

Answer:

Selma need 42 stickers to decorate every unit of the whole journal cover

Explanation:

Selma is decorating the cover of her journal with stickers

The cover is 6 units by 7 units

We need to find area of the journal cover

6 x 7

Breaking apart 7 as 3 ad 4

Area = 6 x ( 3 + 4 )

= (6 x 3) + (6 x 4)

= 18 + 24

= 42

So, area of the cover is 42 square units

Each sticker covers 1 square unit

So, Selma need 42 stickers to decorate every unit of the whole journal cover.

**What fraction of the total area Â¡s red? Write the fraction.**

Question 12.

Answer:

\(\frac{1}{4}\)

Explanation:

There are 4 equal parts in the whole

1 part of the whole is shaded

So, the fraction that represents the shaded part is \(\frac{1}{4}\).

Question 13.

Answer:

\(\frac{1}{8}\)

Explanation:

There are 8 equal parts in the whole

1 part of the whole is shaded

So, the fraction that represents the shaded part is \(\frac{1}{8}\)

Question 14.

Answer:

\(\frac{1}{6}\)

Explanation:

There are 6 equal parts in the whole

1 part of the whole is shaded

So, the fraction that represents the shaded part is \(\frac{1}{6}\)

**Find the perimeter.**

Question 15.

Answer:

27 m

Explanation:

Perimeter of the triangle is sum of all the sides

That is 9 + 9 + 9

So, perimeter is 27 m.

Question 16.

Answer:

8 cm

Explanation:

Perimeter of the square is sum of all the sides

That is 2 + 2 + 2 + 2

So, perimeter is 8 cm.

Question 17.

Answer:

26 ft

Explanation:

Perimeter of the rectangle is sum of all the sides

Opposite sides of the rectangle are equal in lengths

That is 9 + 9 + 4 + 4

So, perimeter is 26 ft.

**Find the length of the unknown side.**

Question 18.

perimeter: 19 m

unknown side: _____________

Answer:

Unknown side = 5 m

Explanation:

Given perimeter = 19 m

Perimeter of a shape is sum of all the sides

4 + 3 + 4 + 3 + ? = 19

14 + ? = 19

19 – 14 = 5

So, unknown side = 5 m.

Question 19.

perimeter: 15 in

unknown side: ______________

Answer:

Unknown side = 6 in

Explanation:

Given Perimeter = 15 in

Perimeter of the triangle is sum of all the sides

That is 3 + 6 + ? = 15

9 + ? = 15

15 – 9 = 6

So, unknown side = 6 in.

Question 20.

perimeter: 13 ft

unknown side: _______________

Answer:

Unknown side = 3 ft

Explanation:

Given perimeter = 13 ft

Perimeter of a shape is sum of all the sides

2 + 2 + 2 + 4Â + ? = 13

10 + ? = 13

13 – 10 = 3

So, unknown side = 3 ft.

**Use the picture to help you solve.**

Question 21.

An artist charges $8 for each square unit of surface space that she paints. How much did she charge for this painting?

Answer:

$80

Explanation:

An artist charges $8 for each square unit of surface space that she paints

The area of the painting is 2 x 5 = 10 square unit

So, multiply 10 with $8 to find the amount the artist charged for the painting

10 x $8 = $80

So, the artist charged $80 for this painting.