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WAEC Further Mathematics 2019 Question 15

Question 15

Matrices and Determinants

If P = (2 3 / −4 1), Q = (6 / 8) and PQ = k(45 / −20), find the value of k. (Matrices written row by row; / separates the rows.)

  1. A.−5/4
  2. B.−4/5
  3. C.4/5
  4. D.5/4
Show the answer and explanation

Answer: C (4/5)

Explanation

PQ = (12 + 24 / −24 + 8) = (36 / −16) = (4/5)(45 / −20), so k = 4/5.