If 16 friends share 4 cupcakes, and each friend gets 4 pieces, you would need to cut each cupcake in 16th's to result in 64 pieces; 64/4 = 16
Simple (Cross multiplication )
7 x
_ _ = 700/8 = 87.5 (100-87.5 = 12.5 is the missing value.
8 100
One method that I use often is to bounce the decimal point over and multiply by 2. ex/ total is 23.52, bounce the decimal between the 2 and 3 to get 2.30 then multiply by 2 giving you 4.60.
or take the total 23.52 and multiply it by .20 which will give you 4.70
The answer is 220 because you would just have to round 1 to 2 than everytging behind it is a zero