HOW TO FIND THE COMMON DENOMINATOR FOR
3/4,3/3,3/8,3/5,3/16,3/7,3/1
The common denominator must be that number into which all the denominators divide evenly,
4 = 2x2
3 = 3
8 = 2x2x2
5 = 5
16 = 2x2x2x2
7 = 4
so we need 2x2x2x2x3x5x7 = 16x3x5x7 = 1680