I like to start with changing fractions to decimals. It seems easier that way.
5/8 = 0.625 cups
Now divide 4 by 0.625
4 / 0.625 = 6.4
Noor can offer 6 cups with an extra 2/5 of a cup left. He can offer the 2/5 of a cup to a friend, so he can offer 7 friends some hot chocolate!