2005 AMC 8 Problem 19

Attempt Problem 19 of the 2005 AMC 8 below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2005 AMC 8 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

19.

What is the perimeter of trapezoid ABCD?ABCD?
180180
188188
196196
200200
204204
Answer: A
Concepts:trapezoidPythagorean Tripleperimeter
Small hint:
Drop perpendiculars to split the trapezoid into right triangles and a rectangle.
Big hint:
Use the 18−24−3018-24-30 and 7−24−257-24-25 right triangles.
Solution:
Drop the altitude from CC to meet AD‾\overline{AD} at FF. The existing altitude from BB meets AD‾\overline{AD} at EE.
By the Pythagorean theorem, AE=302−242=18AE=\sqrt{30^2-24^2}=18 and FD=252−242=7FD=\sqrt{25^2-24^2}=7. Also EF=BC=50EF=BC=50.
Thus AD=18+50+7=75AD=18+50+7=75, and the trapezoid perimeter is 30+50+25+75=18030+50+25+75=180.
Thus, A is the correct answer.
LIVE by Po-Shen Loh
Programs

LIVE Classes

Self-Paced Classes

Stars

Scholarship

About Us

Who Is Po-Shen Loh?

Email Contact

Newsletter

Jobs

Become a Star

For a more Thought Full world.

© 2026 Expii, Inc.