CPM Homework Help : APCALC Problem 10-148

No calculator! $\mathbf{u}=\langle 1,3 \rangle$ , $\mathbf{v}\perp\mathbf{u}$ and $||\mathbf{v}||=10$ . What is $\mathbf{v}$ ?

Compute without a calculator

Hint:

$\overrightarrow{v}=\langle -3c,1c \rangle$

where $c$ is a scalar

More Help:

$\|\overrightarrow{v}\|=\sqrt{(-3c)^2+(1c)^2}$