Write the Perimeter

Part of the Triangles section of Coddy's Geometry journey. Lesson 20 of 71.

So far the equation was given to you. Now you write it from the figure. The perimeter equation is the three side labels added together and set equal to the perimeter. For sides x + 1, 3x and 7 with a perimeter of 24:

$A triangle with sides labelled x plus 1, 3x and 7$

Perimeter 24

(x + 1) + 3x + 7 = 24

Write each side length once in the sum and set the sum equal to the perimeter. This task asks for the equation only, so leave it unsolved.

Write each of the three side lengths once in the perimeter sum. Keep brackets around an expression such as x + 1. Then simplify if you need to. Count the sides in your sum, not the terms. Combining like terms may make the equation shorter, but it must still come from three sides.