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WAEC Mathematics 2011 Question 43

Question 43

Quadratic Equations

In a quiz competition, a student answers n questions correctly and was given D(n + 50) for each question correctly answered. If he gets D600.00 altogether, how many questions did he answer correctly?

  1. A.18
  2. B.15
  3. C.12
  4. D.10
Show the answer and explanation

Answer: D (10)

Explanation

n(n + 50) = 600, so n2 + 50n − 600 = 0 and (n + 60)(n − 10) = 0. n cannot be negative, so n = 10.