CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
If 3^(x+1) = 81, then the value of 2^(x) is:
The value is 8. Since 81 equals 3 to the power 4, x + 1 = 4, so x = 3. Therefore 2 raised to x is 2 cubed, which equals 8.
- A4
- B8Correct
- C16
- D9
Explanation
81 = 3^4, so x+1 = 4 and x = 3. Then 2^x = 2^3 = 8. The option 16 comes from taking x = 4 (using x+1 as x), and 4 from x = 2.
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