Area and perimeter (grade 3) · lesson

Area: the space inside

💡 The area of a rectangle is its length times its width, in square units.

Area counts the squares that cover a shape. A rectangle is rows of squares.

A rectangle 7 long and 3 wide has 3 rows of 7 squares. So multiply length × width.

A square has 4 sides that are all the same. Its area is side × side.

🧠 Let's work it out

A rug is 7 feet long and 3 feet wide. What is its area?

What do you think comes next?

💡 Perimeter is the distance around a shape, so add up all its sides.

Picture an ant walking all the way around the edge. The distance it walks is the perimeter.

A rectangle has two long sides and two short sides. Add all four. A fence or a frame around a shape is its perimeter.

🧠 Let's work it out

A yard is 9 m long and 2 m wide. What is its perimeter?

What do you think comes next?

💡 Work backward from the area or perimeter to find a side you don't know.

If you know the area and one side, ask: this side times what gives the area? That is a divide fact.

If you know the perimeter and the length, take away the two lengths. Half of what is left is the width.

🧠 Let's work it out

A rectangle has a perimeter of 24 cm. Its length is 7 cm. What is its width?

What do you think comes next?

💡 Split a big shape into rectangles, find each area, then add or subtract.

A room shaped like an L is really two rectangles. Find the area of each one and add them.

If a shape has a hole, like a wall with a window, find the whole area. Then take away the area of the hole.

🧠 Let's work it out

A wall is 6 ft by 5 ft. A door cut out of it is 2 ft by 2 ft. What area of wall is left?

What do you think comes next?