There are 44 students in one class. In a math contest, the difference between the average score of boys and girls and the average score of the whole class is 1.5 and 1.8 respectively. How many girls are there in this class? If we use the method of equation, suppose there are X boys and 44-x girls, and the average grade of the whole class is S. According to the meaning of the question, there are.

s * 44 =(s+ 1.5)* x+(s- 1.8)*(44-x)，

solve

1.5*x= 1.8*(44-x)，

So there is

( 1.5+ 1.8)* x = 1.8 * 44 = 79.2，

X=79.2/3.3=24, which means there are 24 boys.

If you don't use the equation method, you can consider it this way. According to the meaning of the question, the average scores of boys and girls are 1.5 and 1.8 respectively. We assume that the average score of boys is lower than that of the whole class 1.5, then the average score of girls is higher than that of the whole class 1.8, which means that the average score of a boy needs 1.5/. So the ratio of the number of boys and girls in the class is1:(1.5/1.8), and the total number of students in the class is 44, so the number of boys is.

44/(1+1.5/1.8) = 24 people.