CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
The value of log₂₅ 125 is:
The value is 3/2. Writing 125 as 5³ and 25 as 5², the change of base gives 3 log 5 divided by 2 log 5, which equals 3/2. The inverted value 2/3 would be log of 25 to the base 125.
- A3/2Correct
- B2/3
- C5/3
- D3
Explanation
log₂₅ 125 = log 5³ / log 5² = 3 log 5 / (2 log 5) = 3/2. The option 2/3 results from inverting the ratio, i.e. computing log₁₂₅ 25 instead.
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