Question

A group of 3 numbers has an average of 17. The first two numbers are 12 and 19. What is the third number? 17 19 20 23 30

Answer 1

Let 3rd no. be x
Therefore (12+19+x)/3=17
31+x=51
x=51-31=20
Therefore x=20
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Answer 2

The third number is 20.

Let the third number be 'x'.

Given,

First number = 12.

Second number = 19

Third number = 'x'.

Sum of the three terms = (12 + 19 + x) = 31 + x

Number of terms = 3

We know, average is given as:

Avg. = (Sum of the terms)/(Number of terms)

= (31 + x)/(3)

Also, average of them is 17.

So, (31 + x) / 3 = 17

⇒ 31 + x = 51

⇒ x = 51 - 31 = 20

'x' is 20.