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3rd grade

Course: 3rd grade > Unit 10

Lesson 4: Multiply to find area
Math
3rd grade
Area
Multiply to find area
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Area of rectangles review

Google Classroom
Review the basics of area of rectangles and try some practice problems.

What is area?

Area is the space inside of a two-dimensional shape. We can also think of area as the amount of space a shape covers.
For example, the rectangle below has an area of 12 square units because it covers 12 square units.
A rectangle with 2 rows. Each row has 6 unit squares. The unit squares are labeled 1 through 12.
Want to learn more about the concept of area? Check out this video.

Area of a rectangle formula

To find the area of a rectangle, we multiply the length of the rectangle by the width of the rectangle.
start text, A, r, e, a, space, o, f, space, r, e, c, t, a, n, g, l, e, end text, equals, start text, l, e, n, g, t, h, end text, times, start text, w, i, d, t, h, end text
Want to know why this formula works? Check out this video.

Example 1:

A rectangle with 2 rows. Each row has 6 unit squares. The left side of the rectangle is labeled 2 units and the top side of the rectangle is labeled 6 units.
start text, A, r, e, a, end text, equals, start text, l, e, n, g, t, h, end text, times, start text, w, i, d, t, h, end text
empty space, equals, 6, times, 2
empty space, equals, 12, start text, space, s, q, u, a, r, e, space, u, n, i, t, s, end text

Example 2:

A rectangle with the left side labeled 4 units and the top side labeled 7 units.
start text, A, r, e, a, end text, equals, start text, l, e, n, g, t, h, end text, times, start text, w, i, d, t, h, end text
empty space, equals, 7, times, 4
empty space, equals, 28, start text, space, s, q, u, a, r, e, space, u, n, i, t, s, end text

Practice set 1: Multiply to find area

Problem 1A
  • Current
What is the area of the rectangle?
A rectangle with the left side labeled 6 units and the top side labeled 5 units.
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text
square units

Want to try some more area of rectangle problems? Check out this exercise:
Area of rectangles

Practice set 2: Count square units to find area

Problem 2A
  • Current
What is the area of the shape? Each square in the grid is a 1, times, 1 unit square.
A figure with 4 rows and 4 columns of 11 unit squares connected together on a grid. The top 2 rows each have 4 unit squares. The third row has 2 unit squares. The bottom row has 1 unit square.
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text
square units

Want to try some more unit square problems? Check out these exercises:
Find area by counting unit squares
Transition from unit squares to area formula
Create rectangles with a given area

Practice set 3: Challenge items

Problem 3A
  • Current
This cat and bird picture has an area of 56 square centimeters. The height of the picture is 7 centimeters.
What is the width of the picture?
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3, slash, 5
  • a simplified improper fraction, like 7, slash, 4
  • a mixed number, like 1, space, 3, slash, 4
  • an exact decimal, like 0, point, 75
  • a multiple of pi, like 12, space, start text, p, i, end text or 2, slash, 3, space, start text, p, i, end text
centimeters
A rectangular picture of a cat and a bird. The left side of the picture is labeled 7 centimeters and the top side of the picture is labeled width.

Want to try some more challenge items? Check out these exercises:
Find a missing side length when given area
Decompose figures to find area 1
Decompose figures to find area 2

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