passwella.
Menu

JAMB Mathematics 1978 Question 11

Question 11

Triangles and Quadrilaterals

In the figure below, FD//AC. The area of AEF = 6sq.cm, AE = 3cm, BC = 3cm, CD = 5cm, <BCD is an obtuse angle. Find the length of BD.

Diagram for this question
  1. A.√33
  2. B.6
  3. C.4
  4. D.2√13
  5. E.4√5
Show the answer and explanation

Answer: D (2√13)

Explanation

½ × 3 × h = 6 gives the distance between the parallel lines h = 4cm. From CD = 5cm, D is 3cm beyond C along the line, so BD is the hypotenuse of a right triangle with sides 4 and 3 + 3 = 6: BD = √52 = 2√13.