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WAEC Mathematics 2010 Question 41

Question 41

Mensuration of Solids

The diagram is a net of a right rectangular pyramid. Calculate the total surface area.

Diagram for this question
  1. A.208 cm2
  2. B.112 cm2
  3. C.92 cm2
  4. D.76 cm2
Show the answer and explanation

Answer: C (92 cm2)

Explanation

Base 8 × 5 = 40. The triangles on the 5 cm sides have height (16 − 8)/2 = 4 cm and those on the 8 cm sides have height (13 − 5)/2 = 4 cm. Total = 40 + 2(½ × 5 × 4) + 2(½ × 8 × 4) = 40 + 20 + 32 = 92 cm2.