Pat starts with two identical square pieces of paper. On the first one, she draws straight lines that divide the paper into a $3$-by-$3$ grid of squares. The total length of the lines she draws is $18 \text{ cm}.$ On the second piece of paper, Pat draws straight lines that divide the paper into a $6$-by-$6$ grid of squares. What is the total length of the lines that Pat draws on the second piece of paper?
Hints --
Draw a 3 x 3 grid -- How many lines did you draw?
What is the total length of the lines?
So, how long must each line be?
Draw a 6 x 6 grid -- How many lines did you draw?
Is each line the same length as the line that you drew for the 3 x 3 grid?
So, how long is the total length?