Perimeter | Adding the lengths by collecting like terms

In the diagram, all measurements are given in centimetres.

All angles are right angles.

Show that the perimeter of the shape can be written as 2(3x + 5).

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Solution

perimeter = side 1 + side 2 + side 3 + ...... (two sides are missing)

                = 2x + x + 3 + 2 + horizontal missing side + vertical missing side

                = 2x + x + 3 + 2 + 2x + 3 + x + 2

                = 6x + 10

                = 2(3 + 10) ......you've got to factorise to show

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Note: to get 4 full marks for this question, student must show (by calculation).