Question

The mid-value of a class interval is 42. If the class size is 10, then the upper and lower limits of the class are:

विकल्प

• 47 and 37

• 37 and 47

• 37.5 and 47.5

•  47.5 and 37.5

Answer 1

Let l and m respectively be the lower and upper limits of the class. Then the mid-value of the class is`(l+m)/2`  and the class-size is (l-m) .

Given that the mid-value of the class is 42 and the class-size is 10. Therefore, we have two equations

`(l+m)/2 =42`

`⇒ l +m = 84,`

m- l =10

Adding the above two equations, we have

`(l+m) +(m-l)= 84+10`

`⇒l+m+m-l=94`

`⇒2m = 94`

`⇒ m = 47`

Substituting the value of m in the first equation, we have

`l+47= 84`

`⇒l= 84-47`

`⇒ l = 37`