What is the value of log5 10 × log10 15 × log15 20 × log20 25?

C. 2 — log5 10 × log10 15 × log15 20 × log20 25=log10log5×log15log10×log20log15×log25log20=log25log5=2log5log5=2

Number system — Question 6

SSC CGL · Quantitative Aptitude

What is the value of log₅ 10 × log₁₀ 15 × log₁₅ 20 × log₂₀ 25?

Correct answer: C

log5 10 × log10 15 × log15 20 × log20 25

$\begin{array}{l} = (\frac{\log 10}{\log 5}) \times (\frac{\log 15}{\log 10}) \times (\frac{\log 20}{\log 15}) \\ \times (\frac{\log 25}{\log 20}) \end{array}$

$= \frac{\log 25}{\log 5} = \frac{2 \log 5}{\log 5} = 2$

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Number system — Question 6

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