Question

the mean of three numbers is 12 two of the numbers are 9 and 14 what is the third number?​

Answer 1

To find : third number .

Given : mean of three numbers is $12$ two of the numbers are $9$ and $14$ .

Solution :

• As per given data we know that mean of three numbers is $12$ two of the numbers are $9$ and $14$ .
• Let , missing number be $x$ .
• Average or mean is the arithmetic mean.
• It is the ratio of sum of all the numbers given in data to the total number of observations.
• Formula: $Average =\frac{\text { sum of all the observations }}{\text { total of observations }}$
• Here, sum of observations = $9 + 14 + x = 23 + x$  
• Total number of observations $=3$
• Substituting values in above formula,

      $12=\frac{23 + x}{3} \\36 = 23 + x \\x = 36 -23 \\x = 13$

Hence , third number is $13$ .

Answer 2

The third number is 13

Explanation:

Given:

1. The mean of three numbers is 12

2. Two of the numbers are 9 and 14

To find:

The third number?​

Mean = Sum of the given Numbers/ Total numbers

Let,

a = First Number

b = Second Number

c = Third Number

a = 9

b = 14

c =?

Mean = 12

Substitute these values in the formula

Mean = Sum of the given Numbers/ Total numbers

Mean = a+b+c/3

Mean = 9+14+c /3

12 = 9+14+c/3

12 = 23+c/3

12×3 = 23+c

36 = 23+c

c = 36-23

c = 13

The third number is 13

Mean = a+b+c/3

12 = (9+14+13)/3

12 = (23+13)/3

12 = 36/3

12 = 12