Surface Area

Surface Area

• Refers to how many square units it takes to cover a surface

4 squares wide

4 squares long

Surface area of a Rectangle or Square

• Formula

• A= Length times width

• Or

• A = L X W

Surface area of a Rectangle or Square

• Example

• A= LW

• = (3m)(5m)

• = 15 m²

3 meters

5 meters1 meter

1 meter

Try

9 cm

2 cm

A = LW

= (9 cm)(2cm)

= 18 cm²

Irregular Shapes

12 m

5 m

4 m

4m

6m

3m1. Cut the

object into regular shapes

2. Apply your formula to each shape

3. Add all the shapes together

Irregular Shapes

12 m

5 m

4 m

4m

6m

3m

1. Give each shape a name and apply it to the formula

2. Example

Aa= LW

Ab= LW

Ac=LW

Irregular Shapes

12 m

5 m

4 m

4m

6m

3m12 m

3 m

Aa= LW = (12m)(3m) = 36m²

Irregular Shapes

12 m

5 m

4 m

4m

6m

3m

Ab= LW = (5m)(3m) = 15m²

5 m

3m

Irregular Shapes

12 m

5 m

4 m

4m

6m

3m

Ac= LW = (4m)(4m) = 16m²

4 m

4m

Irregular Shapes

• Add all the areas together to get a final answer

• Aa + Ab + Ac =

• 36m² + 16m² 15m² = 67m²

Irregular Shapes Continued

• Sometimes you may have to subtract two areas.

• What is the area of the

green squaresquare that is

Remaining?

5 km

Irregular Shapes Continued

What do we know?

- it’s a square which means

all sides are 5km long

What is the diameter

of the circle?

- it’s the width of the square

5 km

5 km

Irregular shapes

• As(s for square) = LW

= (5km)(5km)

= 25 km²

• Ac( for circle) = π r²

= (3.14)(2.5m)²

= 19.625 km²

Irregular Shapes

• Subtract the two areas to get a final answer.

25 km²

- 19.625 km²

5.375 km²