CA Foundation · Quantitative Aptitude · Ratio and Proportion, Indices and Logarithms
The value of log₁₀ 5 + log₁₀ 20 is:
The sum of logarithms with the same base equals the logarithm of the product. So log₁₀ 5 + log₁₀ 20 = log₁₀ 100, and because 10 squared is 100, the value is 2.
- A1
- B2Correct
- Clog₁₀ 25
- D10
Explanation
log 5 + log 20 = log(5 × 20) = log 100 = 2, since 10² = 100. Option 1 would come from wrongly treating the sum as log 10. Option log₁₀ 25 comes from adding 5 and 20 inside the log instead of multiplying.
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