Question

Evaluate:
${\log }_{2}8+{\log }_{5}25$

• A. $5$
• B. $3$
• C. $4$
• D. $10$

Answer 1

The correct option is A $5$

We know that,
${\log }_{a}a=1$ and ${\log }_a{b}^3=3{\log }_{a}b$

Using above identities, we can solve given expression:
${\log }_{2}8+{\log }_{5}25={\log }_2{2}^3+{\log }_5{5}^2$
$=3{\log }_{2}2+2{\log }_{5}5$
$=3\left(1\right)+2\left(1\right)$
$=5$

${\log }_{2}8+{\log }_{5}25=5$