Question

Class	0-10	10-20	20-30	30-40	40-50
Frequency	5	$x$	15	16	6

The missing frequency marked $x$ of the above distribution whose mean is 27 is :

• A. $7$
• B. $8$
• C. $9$
• D. $10$

Answer 1

Answer: (B)

$8$

Class	Frequency (f)	Class Mark (x)	fx
0-10	5	5	25
10-20	x	15	15x
20-30	15	25	375
30-40	16	35	560
40-50	6	45	270
Total	42 + x		1230 + 15x

Given, Mean $=\frac{\sum fx}{\sum f}=27$

$=>\frac{1230+15x}{42+x}=27$

$=>1230+15x=1134+27x$

$96=12x$

$x=8$