Not all fabric tears easily, when I did the sashing for dd's quilt I cut really long strips from my yardage.
Which way do you want to cut it? I'll assume final dimension to be 30 X 180" (5')
Iron it, being very careful not to wrinkle it. Now fold it in half 60" X 90" Line up the ends and edges exactly. Then fold it one more time 60" X 45" Make sure the edges are all lined up! (or trim them if you have a little extra you so you can cut the edges to match) Place on your cutting mat and cut as long as your quilters rule lets you cut, press firmly with the rotary cutter to ensure you cut through all four layers (my mat is 24" X 36" and my longest rule is 6.5" X 24") now gently side the fabric over your cutting surface (if you don't have a flat table big enough for it to lay flat the entire time do it on the floor) and cut the remaining 21" Vola it's in half.