We can split up the 4 fluid answers of paint into fifths. Since there are 5 fifths to one fluid ounce, there are 20 fifths in 4 fluid ounces. There are 5 students, so each gets a fifth of 20 fifths, that is, 4 fifths each.
For each fluid ounce each student gets a fifth, so for 4 fluid ounces each student gets 4 fifths:
4×1/5=4/5.