The following table shows the first math scores of 20 students in a class: 50 60 70 80 90 students: 1 4 x y 2.
The total number of people is 20: 1+4+x+y+2=20, and the average score is 73:1× 50+4× 60+x× 70+y× 80+2× 90 = 20× 73.
X=5 y=8 to solve this equation.
It can be seen that the mode is 80 points (80 points is the maximum number), the sample size is 20 people, the median is the average of 70 points in the tenth place and 75 points in the eleventh place, and a-b=5.