CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
The value of log₅ 125 + log₅ (1/5) is:
The value is 2. Since 5³ = 125, log₅ 125 equals 3, and since 1/5 = 5⁻¹, log₅ (1/5) equals −1. Adding them gives 3 − 1 = 2. Ignoring the negative sign would wrongly give 4.
- A1
- B2Correct
- C3
- D4
Explanation
log₅ 125 = 3 because 5³ = 125. log₅ (1/5) = −1 because 5⁻¹ = 1/5. Sum = 3 − 1 = 2. The option 4 comes from adding 3 and 1 instead of subtracting.
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