Question

If the mean of 5,7,9,X,11,12 is 9 , find the value of X

Answer 1

$\huge{\mathcal{\green{\underline{Answer}}}}$

Mean = Sum of all observations / number of all observations

$mean = 5 + 7 + 9 + x + 11 + 12 \div 6 \\ 9 = \frac{44 + x}{6} \\ 54 = 44 + x \\ 54 - 44 = x$

$\huge{\mathcal{\blue{\underline{x=10}}}}$

Answer 2

Given ,

$\star$Observation = 5 , 7 , 9 , x , 11 , 12

$\star$Mean of the observation = 9

We have to find the value of x , so

$\large\fbox{ \fbox{ \sf \: Mean = \frac{Sum \: of \: terms }{Number \: of \: terms} \: }}$

$\implies \sf 9 = \frac{5 + 7 + 9 + X + 11 + 12}{6} \\ \\\implies \sf 54 = 44 + x \\ \\\implies \sf x = 54 - 44 \\ \\\implies \sf x = 10$

Thus , 6 is the required value of x