Question

The marks scored by Rohit in two tests were $65$ and $70$. Find the minimum marks he should score in the third test to have an average of at least $65$ marks.

• A. $60$
• B. $65$
• C. $70$
• D. $75$

Answer 1

The correct option is A $60$

Let Rohit scored $x$ marks in third paper

Then mean of three papers $=\frac{65+70+x}{3}=\frac{135+x}{3}$

But the average of three papers is at least $65$

$\therefore \frac{135+x}{3}\ge 65$

Multiply both sides by $3$, we get

$\frac{135+x}{3}\times 3\ge 65\times 3$

$\Rightarrow 135+x\ge 195$

Add $-135$ on both sides, we get

$135+x-135\ge 195-135$

$\Rightarrow x\ge 60$