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JAMB Mathematics 1997 Question 21

Question 21

Binary Operations

Two binary operations ∗ and ⊗ are defined as m∗n = mn − n − 1 and m ⊗ n = mn + n − 2 for all real numbers m, n. Find the value of 3 ⊗ (4 ∗ 5)

  1. A.60
  2. B.57
  3. C.54
  4. D.42
Show the answer and explanation

Answer: C (54)

Explanation

4 ∗ 5 = 20 − 5 − 1 = 14. Then 3 ⊗ 14 = 42 + 14 − 2 = 54.