Question

The class average for the first social studies test in Molly’s class was $85\%$. 23 students took the test. When the 24th student joined the class and took the same test, the class average went up to $85.5\%$. What grade did the new student earn on the exam?

Answer 1

Average of 23 students $=\frac{sumofmarksof23}{23}=85$
Sum of marks of 23 students, $S=23\times 85$ = 1955
Let marks earned by new student be x
New $average=\frac{S+x}{24}=85.5$
$\Rightarrow \frac{1955+x}{24}=85.5$
$1955+x=24\times 85.5=2052$
x = 2052 – 1955 = 97