Idea 4of 22Builds onArea counts the squares inside
Length × width gives the area
How can you find a rectangle's area without counting every square?
Today you'll discover
- why the squares come in equal rows
- how multiplying counts them
- the rule for any rectangle
Think firstA rectangle 9 cm long and 6 cm wide
What is a quick way to find how many squares cover it?
Decide first, then press Next. Look at one row, then count the rows.
A rectangle 9 squares long and 6 squares tall, sides marked 9 cm and 6 cm. Squares fill it row by row, with row 1: 9 down to row 6: 9 printed beside the rows, and the line 6 rows of 9: 9 × 6 = 54 cm². The last step shows an 8 m by 3 m rectangle.
See the whole ideathe big idea and the key word, in one place
The big idea
The area of a rectangle is length × width: the rows times the squares in each row.
Area = length × width
Multiply the two sides of a rectangle to get its area.
- length9 cm
- width6 cm
- area54 cm²
Easy to get wrongMultiply, do not add. 9 + 6 = 15 counts along two edges only, not the 54 squares inside.
Key words
- length
- how long a rectangle is, usually its longer side
- width
- how wide a rectangle is, usually its shorter side
Ready to use it?
- Find a rectangle's area with length × width.