Question

A group of four numbers has an average (arithmetic mean) of 15. three of the numbers are 18, 11, and 25. what is the other number
Ans: 6 or 9 or 11 or 13 or 14

Answer 1

Answer:

It is 6

Step-by-step explanation:

Let the number be x ,

(x + 18 + 11 + 25 ) / 4 = 15

(x + 18 + 11 + 25 ) =60

x = 60-18-11-25

x=60-54

x=6

Answer 2

Given:

Three numbers = 11, 18 and 25

Arithmetic mean of four numbers = 15

To Find:

The fourth number

Solution:

The total numbers said in question are four, thus -

Let the fourth number be = x

Given that AM is 15, substituting the values into the formula -

= 18 + 11 + 25 + x  / 4 = 15

= (x + 18 + 11 + 25 ) = 15 x 4

= x + 18 + 11 + 25 = 60

x = 60 - 54

 x = 6

Answer: The fourth number is 6.