Question 468947
If our original 3-cup mixture is 3/5 milk, that means that there are {{{ (3/5)*3=1.8}}} cups of milk.  Once we add 1 cup of milk, we'll have 2.8 cups of milk in the 4 cup mixture.  To turn that into a percent, we'll first divide what we're talking about by the total: {{{ 2.8/4=0.7 }}}  Multiply that decimal by 100, and you get 70%.