Question

If the frequencies of first four numbers out of 1, 2, 4, 6, 8 are 2, 3,3, 2 respectively, then the frequency of 8 if their A.M. is 5, is

• A. 4
• B. 5
• C. 6
• D. none of these

Answer 1

The correct option is C 6

Here, the mean is A = 5.
Let the frequency of 8 be x. Then by the formula
$A=\frac{\sum xf}{\sum f}5=\frac{1.2+2.3+4.3+6.2+8.x}{2+3+3+2+x}=\frac{32+8x}{10+x}or18=3x;\therefore x=6$