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### Course: 3rd grade > Unit 10

Lesson 4: Multiply to find area# Area of rectangles review

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 $12$ square units.

*covers**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.

*Want to know why this formula works? Check out this video.*

### Example 1:

### Example 2:

### Practice set 1: Multiply to find area

### Practice set 2: Count square units to find area

*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

*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

## Want to join the conversation?

- If a shape is uneven, how can we work out the area?(11 votes)
- Try to break the shape into simpler shapes - ones that have areas that are easy to calculate. Calculate the area of each smaller shape, then add them all together to get the area of the whole shape.

(*This is what they did up above when they had us count squares to figure out the area of the big shape.*)

Each square is 1x1, so the area of each square is one.

(*First step: calculating the area of the smaller shapes.*)

Then when we counted all the squares, the total number of squares was also the area of the shape.

(*Second step: add together all the areas of the smaller shapes.*)

Hope this helps!(28 votes)

- How do you figure out square feet? I need to calculate the area of a back splash so i can purchase wall tiles.(30 votes)
- for tiles times the length by the width and you get the area(19 votes)

- what if you reverse the numbers of the area would the answers still be the same?🤔(10 votes)
- It would! For a rectangle, it doesn't really matter which side is length and which side is width. Because the order in which you multiply two numbers doesn't matter, the area is the same both ways. You can think of just turning a rectangle from the skinny side being horizontal to it being vertical. Nothing changes about the amount of space the rectangle takes up, so its area is the same :)(12 votes)

- so let me get this clear, you have to multiply to find the answer?(2 votes)
- To find the area of a rectangle, multiply the length by the width, yes.(13 votes)

- Which would cover more of my floor, a 5m x 6m rug, or a 4m x 8m rug?(0 votes)
- 4m x 8m rug, cause the area of that rug is 32, in contrast to the 5m x 6m rug which is 30.(5 votes)

- What do you do when you have more than 2 missing labels for how many cm. or in. and ft.?(1 vote)
- In Practice 3, the cat picture only has one label. You really only need the area and one side length to solve for all of the lengths.

In the example, the area is 56 cm. One side of the picture is 7 cm. Divide the area by the length, since you know that the product of the two sides will be 56.

56 ÷ 7 = 8.

The missing side is 8 cm.(1 vote)

- i don't really get the first problem in 2A. Cant someone please explain it?(1 vote)
- The shape with the blue outline covers an area equal to that of 11 squares.

Each square has an area of 1 square unit.

So, the area of the shape is 11 square units.(1 vote)

- I dont get Practice Set 3 the last question(1 vote)
- For Practice Set 3 Problem 3(c), you can get the answer simply by the sum of the two unique rectangle area. We can do this as it was mentioned in the question that the figure is made up of 2 rectangle.

And also, we are given the length and width of each unique rectangle! So just find the area of each rectangle, sum both the area of each rectangle up and there, you get the area of the figure! ;)(1 vote)

- How do you figure out square feet? I need to calculate the area of a back splash so i can purchase wall tiles.(1 vote)
- do all of you do this because I don't.(1 vote)

- Is there a formula for a 3d shape?(0 votes)
- Good question! Just like area measures the amount of space (number of unit squares) inside a 2d shape, volume measures the amount of space (number of unit cubes) inside a 3d shape.

The formula for the volume of a rectangular solid (box) is almost like the formula for the area of a rectangle, except that one more dimension (the height) is multiplied. So just as the area of a rectangle is length times width, the volume of a rectangular solid is length times width times height.(2 votes)