An equilateral triangle has a perimeter of 18 feet. If a square whose sides have the same length as one side of the triangle is built, what will be the area of the square?

36 ft²

Step-by-step explanation:

equilateral means all sides are equally long.

a triangle has 3 sides.

in our case they are all equally long.

and their sum (all 3 sides together) is the perimeter

P = 18 = 3 × side length

side length = 18/3 = 6 ft

a square with the same side length (6) had then an area of

side length × side length = 6×6 = 6² = 36 ft²

it is important to remember : a length is measured e.g. in feet (ft). an area is then meshed in square-feet (ft²). it is important to add this to the calculated numbers to express the right dimension of these numbers.