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There are 24 students in the class. The math class is divided into two groups of 12 students on Friday. The table shows the results of pupil assessment in the two groups. Three students in the first group had worse grades than those in the second group. The other students had the same evaluation. What is the arithmetic mean of the grades of all first-group students?

rating	number of students
1	2
2	3
3	6
4	1
5	0

Correct answer:

p =  2.75

Step-by-step explanation:

$$\begin{gathered} s=1\cdot 2+2\cdot 3+3\cdot 6+4\cdot 1+5\cdot 0=30 \\ n=2+3+6+1+0=12 \\ {p}_1=s/n=30/12=\frac{5}{2}=2\frac{1}{2}=2.5 \\ p=(s+3)/n=(30+3)/12=2.75 \end{gathered}$$

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