If 1 cup of milk is added to a 3-cup mixture that is 2/5 flour and 3/5 milk, what percent of the 4-cup mixture of milk?

This is the concept of algebra, the percentage of Milk in the 4 cup mixture will be found as follows;

the ratio of milk to mixture after 1 cup was added to 3-cups was:

1/3

the total ratio of milk in the mixture was:

1/3+3/5

=14/15

thus the percentage of milk will be:

14/15*100

=93 1/3%