Question

IQ of a person is given by the formula
$IQ=\frac{MA}{CA}\times 100$
where, MA is mental age and CA is chronological age. If $80\le IQ\le 140$ for a group of 12 years children, then the range of their mental age is

• A. $9.8\le MA\le 16.8$
• B. $10\le MA\le 16$
• C. $9.6\le MA\le 16.8$
• D. $9.6\le MA\le 16.6$

Answer 1

Answer: (C)

We have
$IQ=\frac{MA}{CA}\times 100$
$\Rightarrow IQ=\frac{MA}{12}\times 100\left[\because CA=12years\right]$
$=\frac{25}{3}MA$
Given, $80\le IQ\le 140$
$\Rightarrow 80\le \frac{25}{3}MA\le 140$
$\Rightarrow 240\le 25MA\le 420$
$\Rightarrow \frac{240}{25}\le mA\le \frac{420}{25}$
$\Rightarrow 9.6\le MA\le 16.8$