1968 AMC 12 Problem 18

Attempt Problem 18 of the 1968 AMC 12 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 1968 AMC 12 solutions, or check the answer key.

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

18.

Side ABAB of triangle ABCABC has length 88 inches. Line DEFDEF is drawn parallel to ABAB so that DD is on segment AC,AC, and EE is on segment BC.BC. Line AEAE extended bisects angle FEC.FEC. If DEDE has length 55 inches, then the length of CE,CE, in inches, is:
514\dfrac{51}{4}
1313
534\dfrac{53}{4}
403\dfrac{40}{3}
272\dfrac{27}{2}
Answer: D
Concepts:similarityangle bisectorparallel lines
Small hint:
Put GG on the extension of AEAE beyond EE, so the bisector condition is ∠FEG=∠GEC\angle FEG=\angle GEC
Big hint:
After showing BE=AB,BE=AB, use similarity of CDECDE and CABCAB
Solution:
Put GG on the extension of AEAE beyond E.E. The bisector condition gives ∠FEG=∠GEC.\angle FEG=\angle GEC. Since FE∥AB,FE\parallel AB, we have ∠FEG=∠BAE.\angle FEG=\angle BAE. Also, rays EGEG and EAEA are opposite, as are rays ECEC and EB,EB, so ∠GEC=∠AEB.\angle GEC=\angle AEB. Thus triangle ABEABE is isosceles and BE=AB=8.BE=AB=8. Similar triangles CDECDE and CABCAB give CECE+8=58.\frac{CE}{CE+8}=\frac58. Hence 8CE=5CE+40,8CE=5CE+40, so CE=403.CE=\frac{40}{3}.
Therefore, the correct answer is D.
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.