Question

In the tables given below, class-mark and frequencies is given. Construct the frequency tables taking inclusive and exclusive classes

Class mark	Frequency
5	3
15	9
25	15
35	13

Answer 1

 Let the Lower class limit and upper class limit of the class mark 5 be x and y respectively.

Class Mark = \(\frac{Lower\, class\, limt \,+\,Upper\, class\, limt \,}{2}\)

\(\therefore\) \(5 =\frac{x\,+\,y}{2}\) 

∴x + y = 10 

Here, class width = 15 – 5 = 10 

But, Class width = Upper class limit – Lower class limit

 ∴ y – x = 10

∴ -x + y = 10 …(ii) 

Adding equations (i) and (ii),

 x+ y = 10 

-x + y = 10 

∴ 2y = 20 

∴ y = 10 

Substituting y = 10 in equation (i),

∴ x + 10 = 10 

∴ x = 0 

∴ class with class-mark 5 is 0 – 10 

Similarly, we can find the remaining classes. 

∴ frequency table taking inclusive and exclusive classes.