Question

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

Answer 1

Let the marks obtained by Ravi in third test be x.

Then average of three tests $=\frac{70+75+x}{3}$

Now $\frac{70+75+x}{3}\ge 60\Rightarrow \frac{145+x}{3}\ge 60$

Multiplying both sides by 3, we have

$145+x\ge 180$

$\Rightarrow x\ge 80-145\Rightarrow x\ge 35$

Thus the minimum marks needed to be obtained by Ravi =35.