Perimeter Flashcards

All 6 cards in this deck

What is the perimeter of a 2D shape?

The total distance all the way around the outside of the shape (add all the side lengths).

What is the formula for the perimeter of a rectangle?

e.g. a rectangle 7 cm by 3 cm

$P = 2 \times (\text{length} + \text{width})$

e.g. $2 \times (7+3) = 20$ cm

How do you find the side length of a square from its perimeter?

e.g. perimeter $36$ cm

Divide the perimeter by 4.

e.g. $36 \div 4 = 9$ cm

What are the steps to find the perimeter of an L-shape when some side lengths are not labelled?

e.g. an L-shape with labelled sides 10 cm, 7 cm, 5 cm and 4 cm

1. Find the missing lengths from opposite sides: $10-4=6$ and $7-5=2$
2. Add every side once around the outside: $10+7+4+5+6+2$
3. Give the answer in length units: $34$ cm

True or false? Perimeter is measured in square units such as cm$^2$.

False. Perimeter is a length, so it is measured in mm, cm, m etc.; only area uses square units.

True or false? Two rectangles with the same area must have the same perimeter.

False. e.g. a $1$ cm by $12$ cm and a $3$ cm by $4$ cm rectangle both have area $12$ cm$^2$ but different perimeters.