Area of a Rectangle
Establish the formula for the area of a rectangle and use it to solve practical problems.
Read this first
Count one row, then count the rows. That is why area is length times width.
Four rows of six squares makes 24.
Words you need
- Area
- The space inside a shape.
- Formula
- A rule written with letters or words.
- Square unit
- A square measuring 1 by 1.
Worked example
e.g. Find the area of a rectangle 6 cm by 4 cm.
- Count the squares in one row. There are 6.
- Count how many rows there are. There are 4.
- So there are 4 lots of 6 squares.
- 4 x 6 = 24 square centimetres.
- That is why the formula is area equals length times width.
Always use square units for area. Never plain centimetres.
Practice
The pictures fade as you go. By the last few you are on your own.
1Find the area of a 5 cm by 3 cm rectangle.with a picture
Answer15 square cm.
2Find the area of a square with side 4 cm.with a picture
Answer16 square cm.
3A rectangle has area 30 and length 6. Find its width.with a hint
Need a hint?
What times 6 makes 30?
Answer5.
4A room is 4 m by 3 m. How much carpet is needed?with a hint
Need a hint?
Use the formula.
Answer12 square metres.
5Find the area of a 7 m by 2 m rectangle.on your own
Answer14 square metres.
6A rectangle has area 24. Give two possible side pairs.on your own
Answer4 and 6, or 3 and 8.
7Why is area measured in square units?on your own
AnswerYou are counting squares.
Think about it
1
Why does length times width give the area?
One good answerIt counts the rows and how many are in each row.
2
Can two rectangles have the same area but look different?
One good answerYes. 2 by 12 and 4 by 6 both give 24.
Common mistakes
Adding the sides instead of multiplying.
Adding gives the perimeter, not the area.
Using cm for area.
Area is in square cm.