Grade: Grade 3 Subject: Mathematics Unit: Area & Perimeter SAT: Geometry+Trigonometry ACT: Math

Guided Practice: Area & Perimeter

Let's work through area and perimeter problems together, step by step. You'll get hints along the way to help you understand each part of the solution!

Quick Formula Reference

Remember These Formulas!

Area = L x W
Rectangle Area
P = 2L + 2W
Rectangle Perimeter
Area = s x s
Square Area
P = 4 x s
Square Perimeter

Guided Problem 1: Finding Area

1 Rectangle Area Problem

A rectangular garden is 8 feet long and 5 feet wide. What is the area of the garden?
8 feet 5 feet 8 feet 5 feet
Step 1 of 3
1 Identify the formula

What formula do we use to find the area of a rectangle?

Area = x

The area formula uses length and width. Think: Area = Length x Width (or just L x W)

2 Plug in the numbers

Now put in the length (8) and width (5) into the formula:

Area = x

The length is 8 feet and the width is 5 feet. So we calculate 8 x 5.

3 Calculate the answer

What is 8 x 5? Don't forget the units!

Area = square feet

Multiply: 8 x 5 = ? Think of 8 groups of 5, or count by 5s eight times: 5, 10, 15, 20, 25, 30, 35, 40.

Excellent! You found the area!

40 square feet

The garden covers 40 square feet of ground.

Guided Problem 2: Finding Perimeter

2 Rectangle Perimeter Problem

Marcus wants to put a fence around his rectangular yard. The yard is 12 meters long and 7 meters wide. How much fencing does he need?
12 m 7 m 12 m 7 m
Step 1 of 3
1 Choose the formula

A fence goes around the outside. Which measurement do we need - area or perimeter?

A fence goes all the way AROUND the yard. Perimeter measures the distance around!

2 Set up the calculation

Using P = 2L + 2W, calculate each part:

2 x 12 =
2 x 7 =

2 x 12 means 12 + 12 = 24. And 2 x 7 means 7 + 7 = 14.

3 Add them together

Now add: 24 + 14 = ?

Perimeter = meters

24 + 14: Start with 24, then add 10 to get 34, then add 4 more to get 38.

Great job! You found the perimeter!

38 meters

Marcus needs 38 meters of fencing to go around his yard.

Guided Problem 3: Square - Both Measurements

3 Square Area and Perimeter

A square tile has sides that are 9 inches long. Find both the area and the perimeter of the tile.
9 in 9 in 9 in 9 in
Step 1 of 4
1 What makes a square special?

How many sides are equal in a square?

sides are equal

A square has 4 corners and 4 sides. All of them are the same length!

2 Find the area

For a square, Area = side x side. What is 9 x 9?

Area = 9 x 9 = square inches

9 x 9 is a perfect square! Count by 9s: 9, 18, 27, 36, 45, 54, 63, 72, 81.

3 Find the perimeter

For a square, Perimeter = 4 x side. What is 4 x 9?

Perimeter = 4 x 9 = inches

4 x 9 = 36. Or think: 9 + 9 + 9 + 9 = 18 + 18 = 36.

4 Compare the answers

Interesting! The area is 81 square inches and the perimeter is 36 inches. Which is larger?

Amazing! You found both measurements!

Area = 81 sq in | Perimeter = 36 in

Notice that area and perimeter measure different things - area is the space inside, perimeter is the distance around!

Practice Problems

Now try these problems on your own! Use what you learned in the guided practice.

Problem 1

A rectangle is 6 cm long and 4 cm wide.
What is the AREA?

Problem 2

A rectangle is 6 cm long and 4 cm wide.
What is the PERIMETER?

Problem 3

A square has sides of 7 feet.
What is the AREA?

Problem 4

A square has sides of 7 feet.
What is the PERIMETER?

Problem 5

Emma wants to put ribbon around a photo.
The photo is 10 inches by 8 inches.
How much ribbon does she need?

Problem 6

A rectangular rug is 9 feet by 6 feet.
What is the area of the rug?

Problem 7

A rectangular pool is 15 meters long and 10 meters wide.
What is the perimeter?

Problem 8

A square garden has an area of 64 square feet.
What is the length of each side?

What We Practiced

1

Identify

Read the problem and decide: Area or Perimeter?

2

Formula

Choose the right formula for the shape.

3

Calculate

Plug in numbers and do the math step by step.

4

Units

Always include the correct units in your answer!

Remember: Area uses SQUARE units (like square feet) because we're measuring space inside. Perimeter uses regular units (like feet) because we're measuring distance around!

Next Steps

  • Review the formulas until you know them by heart
  • Practice identifying whether a problem asks for area or perimeter
  • Try measuring real objects at home and finding their area and perimeter
  • Move on to Word Problems for more practice with real-world scenarios!