Question

Class mark of a class is 30 and class length is 36 in a grouped frequency distribution. The lower boundary of the class is ______.

• A. 36
• B. 48
• C. 12
• D. 16

Answer 1

The correct option is C 12

Let,
lower boundary = x
upper boundary = y
$Classmarks=\frac{\text{upper boundary + lower boundary}}{2}$
30 = $\frac{\text{x+y}}{2}$

x+y = 60 ......................(1)

$Classlength=Upperboundary-Lowerboundary$
36 = y - x .......................(2)
y - x = 36 .......................(2)

Adding equation (1) and (2), we get
2y = 60 + 36 = 96
So, y = 48
By using equation (1), x = 60 - 48 = 12