Question

Sanjay needs 90 meters of fence to go around a rectangular garden.
The length l of the garden is three times its width w.

Three of these equations give the correct value for w.
Which equation does NOT?



w+3w=90

w+3w+w+3w=90

2⋅w+2⋅3w=90

2⋅(3w+w)=90

Answer 1

To find the perimeter of a rectangle you can multiply the length by 2 and the width by 2, or you can add the four sides together.

The wrong equation is w + 3w = 90 because it only has one width and one length, which would be half the total perimeter.