Measurement
Area and perimeter
Work out the area and perimeter of a rectangle.
Perimeter and area answer two different questions about the same shape. The perimeter is the distance all the way round the edge — the length of fence you would need. The area is the amount of flat space inside — the number of square tiles it would take to cover it.
The rule
For a rectangle, area is length × width, and perimeter is every side added up. Because opposite sides of a rectangle match, the perimeter is also length + width, doubled.
Worked example
A rectangle is 7 cm long and 4 cm wide. What are its area and its perimeter?
Area: 7 × 4 = 28.
Seven tiles along each of four rows. Multiplying is just a fast way of counting them.
Watch out
Area is counted in square units and perimeter in ordinary ones, because one measures covering and the other measures walking. Two rectangles can have the same perimeter and completely different areas.
Try it together
Let us work out the area and perimeter of a rectangle 9 cm long and 3 cm wide.
Two questions, two rules. Give just the numbers.
1.Work out the area, in square centimetres.
Have a go
Have a go on your own: a rectangle is 10 cm long and 4 cm wide. What is its perimeter, in centimetres?
Hint: Two lengths and two widths.
Ready to practise?
Eight questions on what you have just read. Nothing is timed, and you can play as many times as you like.