Question

if mean of the data set { 10, 20, 30. x} is 20. then value of x is
А
30
B
20
С C
10
D
15​

Answer 1

Given :

•The mean of the data set is 10,20,30,x is 20

To Find :

•The value of x =?

Formula :

$\boxed{\bf{Mean=\dfrac{sum \: of \: the \: terms}{number \: of \: the \: terms} }}$

Solution :

•Given data is 10,20,30,x

By using formula :

$\\ \implies\sf{Mean=\dfrac{sum \: of \: the \: terms}{number \: of \: the \: terms}}$

Substituting the given values :

$\\ \implies\displaystyle\sf{Mean=\dfrac{10+20+30+x}{4} }$

$\\ \implies\displaystyle\sf{10=\dfrac{60+x}{4} }$

$\\ \implies\displaystyle\sf{10= \dfrac{60+x}{4} }$

$\\ \implies\displaystyle\sf{60+x=40}$

$\\ \implies\displaystyle\sf{x=40-60=-20}$

$\\ \implies\boxed{\displaystyle\sf{x=-20}}$

•The value of x is -20 .