The average of 4 numbers is 30.if the sum of first 3 numbers is 85. the forth number is.
A) 30
B)35
C)45
D)55
Answers
Answer:
ANSWER WITH FULL EXPLANATION
Average of four numbers = 30
Sum of the first three numbers = 85
Let the fourth number be xx .
Now, all the four numbers include the three numbers (whose sum is 85) and the fourth number xx .
So, sum of four numbers = 85+x85+x
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
⇒ \frac{85+x}{4}=30
4
85+x
=30
Multiplying both sides of the equation by 4.
\frac{85+x}{4}*4=30*4
4
85+x
∗4=30∗4
⇒ 85+x=12085+x=120
Subtracting 85 from both sides.
85+x-85=120-8585+x−85=120−85
⇒ x=35x=35
∴ The fourth number is 35.
Hope this may help you.
If you have any doubt, then you can ask me in the comments.
Answer:
35
Step-by-step explanation:
total sum of 4 number is 4x30=120
and 3 no is 85
so 120 — 85 = 35
and this is forth no.