4. An example of this is #5. It can help you figure out what the greatest amount you can have is.
5. 14 boys and 21 girls. 14 + 21 = 35 Find the multiples of 35. { 1, 5, 7, 35 } Obviously 35 can't be used, because there will be only 1 group. So the greatest number of groups would be 7, each containing 5 students.