Question

Consider the following observation table:

Observation	Frequency
1	15
2	10
3	20
4	X

It is known that the sum of average and the total frequency is 52.5
What is the value of X?

• A.
  2
• B.
  5
• C.
  8
• D.
  10

Answer 1

The correct option is B

5
We know,
$Average=\frac{Sumofalltheobservations}{Totalnumberofobservations}$

$\therefore$ $Average=\frac{1+2+3+4}{4}=\frac{10}{4}=2.5$

Total frequency from the table = 45 + X

We know, Average + total frequency = 52.5
$\Rightarrow$ 45 + X + 2.5 = 52.5
$\Rightarrow$ 47.5 + X = 52.5
$\Rightarrow$ X = 5

Hence, X = 5.