Mean proportional between 9 and 16 — Aptitude Question
Mean proportional between 9 and 16: What is the mean proportional between 9 and 16? Answer and worked solution on CodeKairo.
- Topic: Ratio & Proportion
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 40 seconds
Question
What is the mean proportional between 9 and 16?
Options
- 12
- 12.5
- 24
- 25
Show the answer and the worked solution
Correct answer: A. 12
Worked solution
- Mean proportional = √(9 × 16) = √144 = 12.
Answer: 12.
The idea
The mean proportional is the geometric mean, not the arithmetic one — 12, not 12.5. That distinction is exactly what the second option is testing.
Shortcut. √(9 × 16) = √9 × √16 = 3 × 4 = 12 — no need to multiply out to 144.
Common trap. "12.5" — taking the arithmetic mean (9 + 16)/2 instead of the geometric mean.