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WAEC Mathematics 2001 Question 47

Question 47

Mensuration of Solids

The diagram shows a triangular prism of length 7 cm. The right-angled triangle PQR is a cross-section of the prism. |PR| = 5 cm and |RQ| = 3 cm. What is the area of the cross-section?

Diagram for this question
  1. A.4 cm2
  2. B.6 cm2
  3. C.15 cm2
  4. D.20 cm2
Show the answer and explanation

Answer: B (6 cm2)

Explanation

PR is the hypotenuse, so PQ = √(25 − 9) = 4 cm. Area = ½ × 4 × 3 = 6 cm2.