Answer:
The mean of 25 students is 17.6
Step-by-step explanation:
The formula of the mean (average) is mean (average) = [tex]\frac{S}{N}[/tex] , where S is the sum of the data, and N is the number of the data
∵ The average marks of the first 10 students are 17
- That means the mean is 17 and the number of students is 10
∴ Average = 17
∴ N = 10
∵ Average = [tex]\frac{S}{N}[/tex]
- Substitute average by 17 and N by 10
∴ 17 = [tex]\frac{S}{10}[/tex]
- Multiply both sides by 10
∴ 170 = S
∴ The sum of the marks of the first 10 students is 170
∵ The average of the next 15 students is 18
∴ Average = 18
∴ N = 15
- Substitute average by 18 and N by 15
∴ 18 = [tex]\frac{S}{15}[/tex]
- Multiply both sides by 15
∴ 270 = S
∴ The sum of the marks of the next 15 students is 270
Now to find the mean of 25 students and the two sums and divide the answer by 25
∵ S = 170 + 270
∴ S = 440
∵ N = 25
∴ Mean = [tex]\frac{440}{25}[/tex]
∴ Mean = 17.6
The mean of 25 students is 17.6
