IQ of a person is given by formula: IQ`=(M A)/(C A)xx100\ ,\ w h e r e\ M A` is mental age and CA is chronological age. If `80lt=I Qlt=140` for a group of 12 year children, find the range of their mental age.

Explanation

When c = 12, we have `IQ=((m)/(12)xx100)=(25m)/(3)`.
`therefore 80leIQle140rArr80le(25m)/(3)le140`
`rArr 80le(25m)/(3)and (25m)/(3)le140`
`rArr(3)/(25)xx80 lem and mle140xx(3)/(25)`
`rArr(48)/(5)lem andm le(84)/(5)`
`rArr 9.6 le m le 16.8`.
Hence, the required mental age for a group of 12-year children is 9.6 years or more and 16.8 years or less.