CMA Foundation · Fundamentals of Business Mathematics and Statistics · Arithmetic Progression and Geometric Progression
The geometric mean of two positive numbers is 12 and one of the numbers is 8. What is the other number?
The other number is 18. For two positive numbers the geometric mean is the square root of their product, so the product is 12 squared, which is 144. Dividing 144 by the known number 8 gives 18.
- A16
- B18Correct
- C24
- D9
Explanation
GM squared equals the product of the two numbers: 12 x 12 = 144. The other number is 144 / 8 = 18. Option 16 comes from wrongly doubling 8, and 24 from doubling the GM instead of squaring it.
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