Question

if the mean of 3,7,11 and
$x$is 9 what is the value of
$x$
​

Answer 1

GIVEN :-

The mean of 3 , 7 , 11 , x is 9

TO FIND :-

Value of x

FORMULA TO KNOW:-

$\bf{Mean} = \bf\dfrac{Sum\:of\:observations}{No\:of\:observations}$

SOLUTION:-

Sum of observations  = 3+ 7 + 11+ x

Sum of observations = 21 + x

No.of observations  = 4

$\bf{Mean} = \bf\dfrac{Sum\:of\:observations}{No\:of\:observations}$

$\bf{9} = \bf\dfrac{21+x}{4}$

9× 4 = 21+ x

36 = 21 + x

36-21 = x

15 = x

Value of x is 15

____________________________

VERIFICATION:-

Substitute value of x The data of mean should be 9

Sum of observations  = 21 + x

x = 15

Sum of observations  = 21 + 15

Sum of observations  = 36

No.of observations  = 4

$\bf{Mean} = \bf\dfrac{Sum\:of\:observations}{No\:of\:observations}$

$\bf{Mean} = \bf\dfrac{36}{4}$

Mean = 9

HENCE VERIFIED