SOLUTION: 1.) The average of 7 numbers is 5. If the average of first six of these numbers is 4, the seventh number is? 2.) Three years ago the average age of a family of 5 member was 27 y

Algebra ->  Finance -> SOLUTION: 1.) The average of 7 numbers is 5. If the average of first six of these numbers is 4, the seventh number is? 2.) Three years ago the average age of a family of 5 member was 27 y      Log On


   

Question 1080685: 1.) The average of 7 numbers is 5. If the average of first six of these numbers is 4, the seventh number is?
2.) Three years ago the average age of a family of 5 member was 27 years. On the addition of a child to the family, the present average age of the family is still 27 years. Find the present age of the child.
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
1.) The average of 7 numbers is 5.
If the average of first six of these numbers is 4, the seventh number is?
let n = the 7th number
%28%286%284%29%2Bn%29%29%2F7 = 5
24 + n = 7 * 5
n = 35 - 24
n = 11 is the 7th number
;
2.) Three years ago the average age of a family of 5 member was 27 years.
let A = average of the 5 people now
then 3 yrs ago
%28%285A+-+5%283%29%29%29%2F5 = 27
%28%285A+-+15%29%29%2F5 = 27
Cancel the 5 and you have:
A - 3 = 27
A = 30 yrs is their present average age
:
"On the addition of a child to the family, the present average age of the family is still 27 years."
let c = the age of the additional child
%28%285%2830%29+%2B+c%29%29%2F6 = 27
multiply both sides by 6
150 + c = 162
c = 162 -150
c = 12 yrs is the present age of the child.