Question

$\sqrt{10}\times \sqrt{15}$ is equal to
A) $6\sqrt{5}$
B) $5\sqrt{6}$
C) $\sqrt{25}$
D) $10\sqrt{5}$

Answer 1

The answer is B. $5\sqrt{6}$

$\sqrt{10}\times \sqrt{15}$

$=\sqrt{2\times 5}\times \sqrt{3\times 5}$

$=\sqrt{2}\times \sqrt{5}\times \sqrt{3}\times \sqrt{5}$

$=(\sqrt{2}\times \sqrt{3})(\sqrt{5}\times \sqrt{5})$

$=\sqrt{6}\times 5$ [$\sqrt{5}\times \sqrt{5}=5$]

$=5\sqrt{6}$