The ratio of boys is: 220/(220+180) = 1 1/20,11.
2. This number is the minimum multiple of 4 and 10, so it is 20, and the answer is 20 pieces.
3. Sugar is water 5/40= 1/8 8 and sugar is sugar water 5/(40+5) =1/99; Water is sugar: 40/(40+5) = 8/9/9.
4. Just find out the greatest common divisor of 48 and 54, and their agreement says 6.
Therefore, each class is divided into six groups (class one has 8 people in each group and class two has 9 people in each group), so there are 9 people in each group at most.