USing the current dimentions of the quilt 41 X 57 if you use a multiplier of 1.5 you will end up with a quilt 61 X 85. If you use a multiplier of 1.75 you will end up with a quilt 72 X 100 ( give or take a 1/2 inch).
You would do the same for purchasing the fabric if it calls for one yard you need 1X 1.75= 1 3/4 yd.
It is easier once you start to cut the strip sets to make a copy of the strip set cutting chart and write the modifed cutting each one to the new dimension so you do not make a mistake of cutting one set or row to the original size ( ask me how I know ....!).