CMA Foundation · Fundamentals of Business Mathematics and Statistics · Ratios, Variations and Proportions
The third proportional to x and 12 is 36. Find the value of x.
The value of x is 4. When 36 is the third proportional to x and 12, the numbers x, 12 and 36 are in continued proportion, so 12 squared equals x times 36. Hence x equals 144 divided by 36, which is 4.
- A3
- B4Correct
- C6
- D9
Explanation
If x, 12, 36 are in continued proportion, then 12² = x × 36. So x = 144/36 = 4. Option 3 would come from using 36/12, the common ratio, instead of the first term.
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