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
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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) (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
= 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
= 27
= 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
= 27
multiply both sides by 6
150 + c = 162
c = 162 -150
c = 12 yrs is the present age of the child.
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