Question
MCQ} In triangle , point lies on side such that . Point lies on segment such that . The line through and , when extended, meets side at point . The ratio equals:
Options
Answer
(A) .
Detailed solution
Place at the origin and use vectors. Let
on with :
on with :
Parametrise line :
For this point to lie on line (i.e., ), the coefficient of must vanish:
$
1 - \dfrac{16t}{25} = 0 ;\Longrightarrow; t = \dfrac{25}{16}.
$
Then
So , meaning , hence
$
AF:FC = 3:5.
$
Cross-check by mass points: Place masses: at mass , at mass so has mass (since ). Place mass at such that , i.e., mass at should be in ratio with mass at , so mass at is and mass at is (consistent up to scale; rescale 's mass from to by dividing by ; equivalently, multiply 's mass by ). To keep arithmetic clean: mass at , at , so at effective mass and at effective mass Then on , masses at and at , so divides in ratio from . \checkmark
Why this is CAT-level: The natural temptation is to use Menelaus on with transversal ----, but choosing the right triangle and getting the signed ratios correct is error-prone under time pressure. Vector / mass-point methods are faster and trap-resistant. Wrong option (C) corresponds to a common Menelaus sign error.
Answer: (A) .