Solution:
Classes and are given.We know that the class mark is generally average of the upper and lower limit of a classes intervals and the classes size is the difference of the upper and lower limits of a classes intervals.
From the data given in the question,
Find the required class mark.
Class mark of
Class mark of
And the class mark of
Class mark of Thus, the class mark of is 17.5 and class mark of is 45.
Hence, option 3 is correct.