Question

Difficulty: MediumPerimeter and Area of Plane Shapes

An equilateral triangle has an area of 163 cm216\sqrt{3}\text{ cm}^2. If a square has the same perimeter as this equilateral triangle, what is the area of the square?

  1. 36 cm236\text{ cm}^2Answer
  2. B
    48 cm248\text{ cm}^2
  3. C
    64 cm264\text{ cm}^2
  4. D
    144 cm2144\text{ cm}^2

Answer

The area of the square is 36 cm236\text{ cm}^2.
Using the area formula for an equilateral triangle Area=34s2=163\text{Area} = \frac{\sqrt{3}}{4}s^2 = 16\sqrt{3}, we determine the side length s=8 cms = 8\text{ cm}. The perimeter of the triangle is 3×8 cm=24 cm3 \times 8\text{ cm} = 24\text{ cm}. Since the square has an equal perimeter of 24 cm24\text{ cm}, each side of the square measures 24 cm/4=6 cm24\text{ cm} / 4 = 6\text{ cm}. The area of the square is therefore 62=36 cm26^2 = 36\text{ cm}^2.

Step-by-Step Solution

1
Find the side length of the equilateral triangle.
Side length s=8 cms = 8\text{ cm}.
The area of an equilateral triangle is given by Area=34s2\text{Area} = \frac{\sqrt{3}}{4}s^2. Setting 34s2=163\frac{\sqrt{3}}{4}s^2 = 16\sqrt{3} yields s2=64s^2 = 64, so s=8 cms = 8\text{ cm}.
2
Calculate the perimeter of the equilateral triangle.
Perimeter P=24 cmP = 24\text{ cm}.
An equilateral triangle has 3 equal sides, so P=3×8=24 cmP = 3 \times 8 = 24\text{ cm}.
3
Determine the side length of the square.
Square side length a=6 cma = 6\text{ cm}.
The square and triangle have equal perimeters (24 cm24\text{ cm}). Since a square has 4 equal sides, a=244=6 cma = \frac{24}{4} = 6\text{ cm}.
4
Calculate the area of the square.
Area =36 cm2= 36\text{ cm}^2.
The area of a square is a2=62=36 cm2a^2 = 6^2 = 36\text{ cm}^2.

Key Concept

Perimeter and Area of Equilateral Triangles and Squares
Estimated Time:1m 30s
Rate this question