Question

I.Q. of a person is given by $I=\frac{M}{C}\times 100$, where $M$ is mental age and $C$ is chronological age. If $80\le I\le 140$ for a group of $12$ years old children, then the range of their mental age is

• A. $[9.6,16.8]$
• B. $(9.6,16.8)$
• C. $[9,16]$
• D. $(9,16)$

Answer 1

The correct option is A $[9.6,16.8]$

$80\le \frac{M}{C}\times 100\le 140$
$\Rightarrow 8\le \frac{M}{12}\times 10\le 14$
$\Rightarrow 96\le 10M\le 168$
$\Rightarrow 9.6\le M\le 16.8$