Question

An irregular polygon with 4 sides is shown.

Select the equation that can be used to find the side length, d, given the perimeter, P , and other three sides.
A
d=P−a−b+c
B
d=P−a−b−c
C
d=P/a−b−c
D
d=P−a+b+c

Answer 1

The correct answer would be b) d=P-a-b-c

You would take the perimeter and subtract the 3 known sides from it to find the missing side.

Answer 2

We know that the sum of the lengths of the sides of a polygon is the perimeter of the polygon, by definition.

Thus, in our case of four sided polygon with the side lengths as a,b,c and d and the perimeter as P, we can write the equation of the perimeter to be as:

`P=a+b+c+d`

Thus, if we have to find the side length, d, given the perimeter, P , and other three sides a,b and c, then we will have to isolate the d in the above equation by subtracting a+b+c from both sides. We will get:

`P-a-b-c=d`

Thus, the the equation that can be used to find the side length, d is:

`d=P-a-b-c`

From the given list Option B is the correct option.