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WAEC Mathematics 2021 Question 20

Question 20

Mensuration of Plane Shapes

In ΔLMN, |LM| = 6 cm, ∠LMN = 90°, ∠LNM = x and sin x = 3/5. Find the area of ΔLMN.

  1. A.60 cm2
  2. B.48 cm2
  3. C.24 cm2
  4. D.30 cm2
Show the answer and explanation

Answer: C (24 cm2)

Explanation

LM is opposite x, so LN = 6 ÷ (3/5) = 10 cm and MN = √(100 − 36) = 8 cm. Area = ½ × 6 × 8 = 24 cm2.