NCERT Class XI Mathematics - Linear Inequalities - Solutions

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Question : 65
Total: 65
IQ of a person is given by the formula
IQ =
MA
CA
× 100
where MA is mental age and CA is chronological age. If 80 ≤ IQ ≤ 140 for a group of 12 years old children, find the range of their mental age.
Solution:  
We have, IQ =
MA
CA
× 100
We are given 80 ≤ IQ ≤ 140
Putting the values of IQ in it.
80 ≤
MA
CA
× 100 ≤ 140
Also we have, CA = 12 years
80 ≤
MA
12
× 100 ≤ 140
Multiplying both sides by 12 ⇒ 12 × 80 ≤ MA × 100 ≤ 140 × 12
or 960 ≤ 100 × MA ≤ 1680
Dividing by 100, 9.6 ≤ MA ≤ 16.8
Hence, mental age is greater than or equal to 9.6 years and less than or equal to 16.8 years.
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