WAEC Mathematics 2018 Theory — Question 15
Question 15 of 23 from the West African Examinations Council (WAEC) Mathematics 2018 Theory paper, with the correct answer and a full explanation.
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9.(b) The base of a right pyramid with vertex V is a square PQRS of side 15cm. If the slant edge is 32cm long: (i) Represent the information in a diagram. (ii) Calculate its Height (correct to 1 decimal place) and Volume (correct to the nearest cm³).
Model answer
Half-diagonal of the square base = (15√2)/2 ≈ 10.6cm. Height² = 32²−10.6² = 1024−112.36 = 911.64, so Height ≈ 30.2cm. Volume = ⅓ × base area × height = ⅓ × 225 × 30.2 ≈ 2265cm³.
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