In a quiz competition, a student answers n questions correctly and was given D(n +...
MATHEMATICS
WAEC 2011
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?
- A. 18
- B. 15
- C. 12
- D. 10
Correct Answer: D. 10
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
Post an Explanation Or Report an Error
If you see any wrong question or answer, please leave a comment below and we'll take a look. If you doubt why the selected answer is correct or need additional more details? Please drop a comment or Contact us directly. Your email address will not be published. Required fields are marked *