Answer:
The class interval is: 20-30
Step-by-step explanation:
Let l be the lower class limit and u be the upper class limit.
Then according to given statement that class mark is 25
[tex]\frac{l+u}{2} = 25\\l+u = 50\ \ \ Eqn\ 1[/tex]
And
Class size is 10
So, the second equation will be:
[tex]u-l = 10\ \ \ \ Eqn\ 2[/tex]
Adding equation 1 and 2
[tex]l+u+u-l = 50+10\\2u = 60\\\frac{2u}{2} = \frac{60}{2}\\u = 30[/tex]
Now putting u =30 in equation 1
[tex]l+u = 50\\l+30 = 50\\l = 50-30\\l = 20[/tex]
A class interval is written in the form that lower limit comes first and upper limit comes second.
So,
20-30
Hence,
The class interval is: 20-30
