CMA Foundation · Fundamentals of Business Mathematics and Statistics · Ratios, Variations and Proportions
If 6, 9 and x are in continued proportion, what is the value of x?
The value of x is 13.5. In a continued proportion the middle term is the mean proportional, so 9 squared equals 6 times x. This gives x = 81/6 = 13.5. A common-difference series such as 6, 9, 12 would wrongly give 12.
- A12
- B13.5Correct
- C15
- D18
Explanation
In continued proportion 6 : 9 = 9 : x, so x = 9 × 9 / 6 = 81/6 = 13.5. The value 12 comes from wrongly using the arithmetic progression, 6, 9, 12, which is not a proportion.
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