Question

The average of 4 number is 30. If three number sum is 85 . what is the fourth number?​

Answer 1

Step-by-step explanation:

a + b + c + d) /4= 30

sum of all four numbers would be 30 * 4 = 120

sum of first three numbers is 85

so 85 + d = 120

d = 120 - 83

d = 35

Answer 2

${\small{\bold{\purple{\underline{Answer}}}}}$

Average of four numbers = 30

Sum of the first three numbers = 85

Let the fourth number be .

Now, all the four numbers include the three numbers (whose sum is 85) and the fourth number .

So, sum of four numbers =

Now, we know that sum of all observations divided by the number of observations is the average of the given data.

Now,

Sum of all four numbers

-------------------------------- = Average

4

⇒

Multiplying both sides of the equation by 4.

⇒

Subtracting 85 from both sides.

⇒

∴ The fourth number is 35.