Question

Prof. Suman takes a number of quizzes for a course. All the quizzes are out of 100. A student can get an A grade in the course if the average of her scores is more than or equal to 90. Grade B is awarded to a student if the average of her scores is between 87 and 89 (both included). If the average is below 87, the student gets a C grade. Ramesh is preparing for the last quiz and he realizes that he will score a minimum of 97 to get an A grade. After the quiz, he realizes that he will score 70, and he will just manage a B. How many quizzes did Prof. Suman take?

A.
6
B.
7
C.
8
D.
9
E.
None of these

Accepted Answer

D. Let $n$ be the total number of quizzes. Difference in Ramesh's last quiz score $= 97 - 70 = 27$. This difference changes his final average from the minimum for A grade ($90$) to the minimum for B grade ($87$), i.e., a change in overall average of $90 - 87 = 3$. Thus, $3 	imes n = 27 \implies n = 9$.

Quiz Average and Grades

Explanation

Practise this under exam conditions