Question

For the following data, mean of x is found to be 7.3. The missing frequency is
x : 5 6 7 8 9
f : 4 6 12 - 8

• A. 10
• B. 9
• C. 8
• D. 7

Answer 1

The correct option is A

10

$Mean=\frac{5\times 4+6\times 6+7\times 12+8\times f+9\times 8}{4+6+12+f+8}$
Where f is the missing frequency
$\Rightarrow 7.3=\frac{20+36+84+8f+72}{30+f}=\frac{212+8f}{30+f}\Rightarrow 219+7.3f=218+8f\Rightarrow 7=.7f\Rightarrow f=\frac{7}{.7}=\frac{70}{7}=10$