Question

The average of four numbers is 30.if the sum of first three numbers is 85,the fourth number is

Answer 1

GiveN :

• Average of first four numbers is 30.
• Sum of three numbers is 85.

To FinD :

• Fourth number

SolutioN :

Let, the fourth number be x.

⇒Average = Sum of Observations/Number of Observations

⇒30 = (85 + x)/4

⇒30 * 4 = 85 + x

⇒120 = 85 + x

⇒x = 120 - 85

⇒x = 35

Hence, Fourth number is 35

Answer 2

AnswEr :

• Fourth number is 35.

GivEn :

• Sum of the 3 numbers = 85

• Average of 4 numbers = 30

To find :

• Fourth number = ?

SoluTion :

Let us assume that the fourth number is x.

Now,

As average is given,

$: \implies \sf \: \: \: Mean = \dfrac{Sum \: of \: Observations}{Number \: of \: Observations}$

$: \implies \sf \: \: \: 30 = \dfrac{85 + x}{4}$

$: \implies \sf \: \: \: 120= 85 + x$

$: \implies \sf \: \: \: x= 120 - 85$

$: \implies \sf \: \: \: { \underline{ \boxed{ \sf{ \purple{x= 35}}}}} \: \bigstar$

Therefore, the fourth number is 35.

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✩ Additional information :

Mean is also referred as average amount in a given group of data.

It is summation of all the observation divided by the number of observations in the given data .

It is given as,

$\dag \: { \boxed{\rm {\: Mean = \dfrac{Sum \: of \: Observations}{Number \: of \: Observations} }}}$

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