Question

On a coordinate plane, trapezoid A B C D has points (negative 3, negative 2), (negative 1, 2), (3, 2), and (5, negative 2).
Figure ABCD is graphed on a coordinate plane.

ABCD is an isosceles trapezoid. What is the approximate perimeter of ABCD? Round to the nearest tenth.

16.5 units
18.9 units
20.9 units
24.0 units

Answer 1

Label the vertices A(−3,−2), B(−1,2), C(3,2), D(5,−2).

Lengths:
- AB = sqrt[(−1+3)^2 + (2+2)^2] = sqrt(2^2 + 4^2) = sqrt(20) ≈ 4.4721
- BC = distance from (−1,2) to (3,2) = 4
- CD = same as AB ≈ 4.4721 (isosceles)
- DA = distance from (5,−2) to (−3,−2) = 8

Perimeter = 8 + 4 + 2·sqrt(20) ≈ 12 + 8.9443 = 20.9443 ≈ 20.9 units.

Answer: 20.9 units.