Question

Simplify the sum or difference: $-6\sqrt{10}+5\sqrt{90}$

• A. $9\sqrt{10}$
• B. $-9\sqrt{10}$
• C. $-39\sqrt{10}$
• D. $-10$

Answer 1

The correct option is A

$9\sqrt{10}$

Explanation for the correct option:

Given that $-6\sqrt{10}+5\sqrt{90}$

By subtracting we get,
$$\begin{gathered} -6\sqrt{10}+5\sqrt{90}=-6\sqrt{10}+5\sqrt{9\times 10} \\ =-6\sqrt{10}+15\sqrt{10} \\ =9\sqrt{10} \end{gathered}$$

Hence option $\left(A\right)$ i.e. $9\sqrt{10}$ is correct.