Question

Average of first three number is twice the fourth number if the average of all the four number is 28 find the fourth number

Answer 1

Let the fourth number be x

So average of first three numbers will be 2x

sum of first three numbers is 2x×3=6x

Average of all four numbers =sum of all numbers /total number

28=6x+x/4

7x=28×4

x=28×4/7

x=4×4

x=16

so the fourth number is 16

Answer 2

The fourth number will be 16.

Step-by-step explanation:

As given in question that average of first three number is twice of the fourth number.

The average of all four numbers is 28.

We have to find the fourth number.

Let the fourth number be x.

According to the question

All first three number will be 2x.

We know that,

$Average = \frac{Sum\ of\ all\ numbers}{Total\ number\ of\ the\ given\ number}$

$28 = \frac{2x\ +\ 2x\ +\ 2x\ +\ x}{4}$

28 x 4 = 7x

$\frac{28\times4}{7} = x$

4 x 4 = x

∴ x = 16

Thus the fourth number will be 16.