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JAMB Mathematics 1978 Question 4

Question 4

Triangles and Quadrilaterals

In the figure below, DE//BC, DB//FE, DE = 2cm, FC = 3cm, AE = 4cm. Determine the length of EC

Diagram for this question
  1. A.4cm
  2. B.6cm
  3. C.3cm
  4. D.2cm
  5. E.1cm
Show the answer and explanation

Answer: B (6cm)

Explanation

DBFE is a parallelogram, so BF = DE = 2cm and BC = 5cm. Triangles ADE and ABC are similar, so AE/AC = DE/BC: 4/(4 + EC) = 2/5, giving 4 + EC = 10 and EC = 6cm.