Forming equations from perimeter

The Maths Habit

A triangle has a
perimeter of 20 cm.
What could its sides be?

5, 7 and 8 cm, for example
(2, 3 and 15 cm will not join up)

Simplify

  1. x + x + 4 + x

    3x + 4

  2. 2x + x + 3 + x

    4x + 3

  3. x + 2 + x + 2 + x + 2

    3x + 6

  4. x + 1 + 2x + x + 5

    4x + 6

Perimeter
The distance around the edge of a shape.
Equation
Two things that are equal, shown with an equals sign.

Perimeter = 19 cm

The perimeter is 27 cm. Find x.

The perimeter is 30 cm. Find x.

x = 8

x + x + 1 + x + 5 = 30

3x + 6 = 30

The perimeter is 24 cm. Find x.

x = 5

The perimeter is 30 cm. Find x.

x = 8

The perimeter is 36 cm. Find x.

x = 9

The perimeter is 30 cm. Find x.

x = 8

The perimeter is 30 cm. Find x.

x = 6

The perimeter is 30 cm. Find x.

x = 8

The perimeter is 39 cm. Find x.

x = 10

The perimeter is 30 cm. Find x.

x = 8

The perimeter is 34 cm. Find x.

x = 7

The perimeter is 24 cm. Find x.

x + 2x

Forming and solving equations: perimeter worksheet, page 1

Forming and solving equations: perimeter worksheet, page 2

Answer sheet

  1. A rectangle has a perimeter of 46 cm. Its length is 5 cm more than its width. Work out its area.

    126 cm2

  2. An equilateral triangle has sides of x + 4. A square has sides of x. They have the same perimeter. Find x.

    x = 12

  1. The sides are in cm and the perimeter is 34 cm. Find x.

    x = 7
    2xx + 1x + 5

  2. An isosceles triangle has two sides of 2x cm and a base of (x + 9) cm. Its perimeter is 29 cm. Find x.

    x = 4

  3. A rectangle is x cm wide and (x + 5) cm long. Its perimeter is 30 cm. Find its area.

    50 cm2
Exit tickets to print