Question

Find the value of: $\log 87600+\log 23100-8 =\ ?$

• A. $\log 8.76 + \log 2.31$
• B. $\log 87.6 + \log 23.1$
• C. $\log 876 + \log 231$
• D. None of these

Hint:

Write numbers in scientific form $a\times10^n$ and use $\log(ab)=\log a+\log b$ to cancel powers of $10$ quickly.

Answer 1

The Correct Option is A

$\log 87600=\log(8.76\times10^4)=\log 8.76+4$;
$\log 23100=\log(2.31\times10^4)=\log 2.31+4$.
So, $\log 87600+\log 23100-8=(\log 8.76+4)+(\log 2.31+4)-8
⇒ \log 8.76+\log 2.31.$