To make a square blanket, you need to calculate the square root of 120, which is 10,954... so the biggest number is 10x10 peaces of fabric you can use to create a square blanket. These are 100 (so 20 are left over). To create a bigger square blanket of 11×11 peaces (11^2 = 121) you need one more peace of fabric. One peace is six inches, the blanket is 10 peaces long (6×10=60) The size would be 60inx60in= 3.600 inches.