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Grade 4 · Maths · Lessons
Area and the way round
🟫rug📏sides🏃round🟦squares
Area and perimeter.
The big ideaArea is length times width. The way round is two lengths and two widths.

How it works

Area is length times width. The way round, the perimeter, is two lengths and two widths.

If you know the area and one side, divide to find the other side.

If you know the perimeter and one side, take two of that side away and halve the rest.

Perimeter• 5 + 4 + 5 + 4 = 18Area• 5 × 4 = 20 square units
Same card, two measures.

Example 1: The way round

  1. The card is 5 centimeters long and 4 centimeters wide. What is its perimeter?
  2. Add two lengths and two widths.
  3. 5 + 4 + 5 + 4 = 18.
  4. So the answer is 18.

Example 2: Find a missing side from area

  1. The area is 480 square meters. One side is 80 meters. Find the other.
  2. Area ÷ the known side.
  3. 480 ÷ 80 = 6.
  4. So the answer is 6.

Example 3: Find a missing side from perimeter

  1. The perimeter is 174 feet. One side is 33 feet. Find the other.
  2. Half of 174 is 87. That is one length plus one width.
  3. 87 − 33 = 54.
  4. So the answer is 54.

Words to know

area
How much flat space a shape covers.
perimeter
The distance all the way round.

Watch out

Try it

  1. A floor is 91 meters long and 30 meters wide. What is its perimeter?
  2. A patio is 17 feet long, 7 feet wide. How many feet of edging?
  3. The area is 342 square meters. One side is 9 meters. Find the other.
Answers: 1. 242 · 2. 48 · 3. 38
For grown-upsFind the area and perimeter of a table top and compare.
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