Question

1 point

If mean of 3,7,11 and x is 9 , what is the value of x?​

Answer 1

Given

We have given mean of 3,7,11 and x is 9.

To Find

We have to find the value of x

$\sf\huge \mathbb{\underline{\underline{{Solution}}}}$

We use mean formulas to calculate x

$\sf \boxed { \: Mean = \dfrac{Sum \: of \: all \: terms}{No \: of \: terms}}$

Numbers =>3,7,11 and x

Number of terms = 4

Sum of all numbers (terms)= 3+7+11+x = 21+x

Mean is given which is 9

Applying mean's formula

$\sf \: Mean = \dfrac{21 + x}{4}$

$\sf\implies 9 = \dfrac{21 + x}{4}$

$\sf\implies \: 21 + x = 9 \times 4$

$\sf\implies \: 21 + x = 36$

$\sf\implies \: x = 36 - 21$

$\sf\implies \: x = 15$

$\sf\therefore \: The \: value \: of \: x \: is\: \red{15}$

Check:

$\sf\implies \dfrac{3 + 7 + 11 + x}{4}$

$\sf\implies \dfrac{21 + x}{4}$

$\sf\implies \dfrac{21 + 15}{4} = \dfrac{36}{4} = 9$

More information=>

• Mean is the average value of all given values /data.
• Symbol of mean is X bar.

There are various types of mean :

• Arithmetic mean
• Geometric mean
• Root mean square
• Harmonic mean
• Contraharmonic mean