A male child of 15 years with a mental age of 12 years has an IQ of –
First, I remember that IQ is calculated using the formula: IQ = (Mental Age / Chronological Age) × 100. So the key concept here is the original IQ formula from Binet and Simon. The question states the child is 15 years old (chronological age) and has a mental age of 12. Plugging those numbers in: (12/15)*100 = 80. So the IQ should be 80.
Now, checking the options. The user didn't list the options, but the correct answer is supposed to be one of them. The possible options might be around 80, 85, 90, or something else. But since the correct answer is 80, I need to make sure that's the case.
Why is this the right approach? Because the formula is standard. Mental age divided by chronological age times 100 gives the IQ score. So if mental age is lower than chronological age, IQ is below 100, indicating some level of intellectual disability, but in this case, 80 is considered mild, but the question is just about calculation.
For incorrect options, if someone thought mental age is subtracted from chronological age, they might get 3, but that's not how it's done. Alternatively, maybe they reversed the ratio, doing 15/12*100=125, which would be higher. Another mistake could be adding them, but that's not correct either. So the wrong options would be based on these calculation errors.
The clinical pearl here is to remember the formula correctly. Students often mix up multiplication/division or subtraction. Emphasizing that IQ is a ratio scaled to 100 is important. Also, note that this formula is from the original Stanford-Binet test, but modern IQ tests use deviation IQ, which is based on standard deviations from the mean. However, for this question, the classic formula applies.
So putting it all together, the correct answer is 80, calculated as (12/15)*100. The explanation should clarify the formula, why other options are wrong, and highlight the key formula to remember.
**Core Concept**
IQ is calculated using the formula: **IQ = (Mental Age / Chronological Age) × 100**. This classical formula from the Stanford-Binet Intelligence Scale assesses cognitive development relative to chronological age.
**Why the Correct Answer is Right**
For a 15-year-old with a mental age of 12: **IQ = (12 / 15) × 100 = 80**. This reflects a mental age lagging 3 years behind chronological age. The result falls in the "low average" range (IQ 70–89), though modern IQ scales use deviation scores with a mean of 100 and SD of 15.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect calculation (e.g., subtracting mental age from chronological age: 15 – 12 = 3).
**Option B:** Misapplication