we need to find out the unit ratio for one of the 16 cups
5.6/16=0.35
now we need to do the same thing with the others and figure out which ones have the same unit ratio
0.7/2=0.35 yes
1.6/4=0.4 no
2.8/8=0.35 yes
3/10=0.3 no
6.3/18=0.35 yes
7/20= 0.35 yes
so, the 2,8,18, and 20 are the same