Skip to content

CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms

If 2^(x) = 5 and the expression 4^(x) − 2^(x+1) is evaluated, its value is:

The value is 15. Since 2^x equals 5, 4^x equals 25 and 2^(x+1) equals 2 times 5, which is 10. Subtracting gives 25 minus 10, which is 15.

  1. A15Correct
  2. B20
  3. C25
  4. D35

Explanation

4^x = (2^x)^2 = 25. 2^(x+1) = 2 × 2^x = 10. So the value is 25 − 10 = 15. The option 35 results from adding instead of subtracting.

Did you get it right without looking?

One question tells you little. A timed set on Ratio and Proportion, Indices and Logarithms shows your real accuracy, how long you take and where you lose marks.

Practise Ratio and Proportion, Indices and LogarithmsFree diagnostic mock

More Ratio and Proportion, Indices and Logarithms questions