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A person's intelligence quotient is defined by IQ = (MA/CA) × 100, where MA denotes mental age and CA denotes chronological age. For a set of 12 children, if 80 ≤ IQ ≤ 140, then the possible interval for their mental age is

1. 9.8 ≤ MA ≤ 16.8
2. 10 ≤ MA ≤ 16
3. 9.6 ≤ MA ≤ 16.8
4. 9.6 ≤ MA ≤ 16.6

Correct answer: 9.6 ≤ MA ≤ 16.8

Solution

From IQ = (MA/CA)*100, MA = IQ*CA/100. With CA = 12: lower MA = 80*12/100 = 9.6 and upper MA = 140*12/100 = 16.8. Hence 9.6 <= MA <= 16.8.

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