I know that the determinant of a matrix is a measure of its area or volume, and that multiplying a row or column by a scalar also multiplies the determinant by that scalar. So, if I multiply both rows of the matrix by 2, I should multiply the determinant by 2^2 = 4. Therefore, $\begin{vmatrix} 2a & 2b \\ 2c & 2d \end{vmatrix} = 4 \cdot \begin{vmatrix} a & b \\ c & d \end{vmatrix} = 4 \cdot 5 = 20.$ 
Given $\begin{vmatrix} a & b \\ c & d \end{vmatrix} = 5,$ find $\begin{vmatrix} 2a & 2b \\ 2c & 2d \end{vmatrix}.$