in a quiz competition, a student answers n questions correctly and was given D(n +…

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?

Correct Answer: Option D

Explanation

let the number of question = n
n(n + 50) = 600
n² + 50n – 600 – 0 by quadratic formular
x = (frac{b pm sqrt{b^2 – 4ac}}{2})
n = (frac{-50 pm sqrt{50^2 – 4(1) (-600)}}{2(1)})
= (frac{-50 pm sqrt{4900}}{2})
= (frac{-50 + 70}{2})
= (frac{20}{2})
= 10