Answer:
Explanation:
The average is the mean. It is calculated adding all the values and dividing the sum by the number of values (data):
For the students who took the test the day before you, you can write:
[tex]mean_1=\sum scores/n[/tex]
Where n is the number of students who took the test first.
Thus, when the average was 69 the equation is:
[tex]69=\sum scores/n[/tex]
When you take the test, the n + 1, the new average is 70, and the sum of the scores raised in 95 points:
[tex]mean_2=(\sum scores + 95)/(n+1)\\ \\ 70=(\sum scores+95)/(n+1)[/tex]
Now you have a system of two equation and two unknowns, so you can solve it.
Clear the sum of the scores from the first equation:
[tex]69=\sum scores/n=>\sum scores=69n[/tex]
Subsitute in the second equation:
[tex]70=(69n+95)/(n+1)[/tex]
Solve for n:
[tex]70(n+1)=69n+95\\ \\ 70n+70=69n+95\\ \\ 70n-69n=95-70\\ \\ n=25[/tex]
Thus, when you include your self the number of students who took the test was 25 + 1 = 26.
