Question

Ravi obtained $70$ and $75$ marks in first two unit test. Find the minimum marks he should get in the third test to have an average of at least $60$ marks.

Answer 1

Let $x$ be the marks obtained by Ravi in the third unit test.
Since the student should have an average of at least $60$ marks.
$\frac{70+75+x}{3}\ge 60$
$\Rightarrow 145+x\ge 180$
$\Rightarrow x\ge 180-145$
$\Rightarrow x\ge 35$
Thus the student must obtain a minimum of $35$ marks to have an average of at least $60$ marks.