For the moment we are finished with \emph{geometric} thinking and are now going to begin playing with numbers and doing arithmetic on terms such as $\sqrt{121}$ and $\sqrt{48}$. You should be able to simplify the former $\sqrt{121} = 11$, but the latter is a little more tricky. Watch this: \(\sqrt{48} = \sqrt{16\times3} = 4\sqrt{3}\). This surd is now considered simplified. \begin{examplebox} \section*{Examples} Try to simplify the following: \begin{multicols}{2} \begin{questions} \Question[1] $\sqrt{18}=\sqrt{9\times2}=3\sqrt{2}$ \Question[1] $\sqrt{108}=\sqrt{36\times3}=6\sqrt{3}$ \Question[1] $\sqrt{45}=\sqrt{9\times5}=3\sqrt{5}$ \Question[1] $\sqrt{32}=\sqrt{16\times2}=4\sqrt{2}$ \end{questions} \end{multicols} \end{examplebox} \begin{exercisebox} \section*{Exercises} Now try going backwards: \begin{multicols}{2} \begin{questions} \Question[1] $3\sqrt{7}=\sqrt{9\times7}=\sqrt{63}$ \Question[1] $5\sqrt{3}=\sqrt{25\times3}=\sqrt{75}$ \end{questions} \end{multicols} \end{exercisebox} You will be doing much more practise with these new mathematical objects in the homework, so do not worry if it feels uncomfortable right now!