SOLUTION: 5 years ago,the average age of p and q was 15 years.average age of p,q and r today is 20 years. how old will r be after 10 years?

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Question 304764: 5 years ago,the average age of p and q was 15 years.average age of p,q and r today is 20 years. how old will r be after 10 years?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
5 years ago,the average age of p and q was 15 years.
average age of p,q and r today is 20 years.
how old will r be after 10 years?
:
"5 years ago,the average age of p and q was 15 years."
%28%28p-5%29%2B%28q-5%29%29%2F2 = 15
%28p%2Bq-10%29%2F2 = 15
multiply by 2
p + q - 10 = 30
p + q = 30 + 10
p + q = 40
:
"average age of p,q and r today is 20 years."
%28p%2Bq%2Br%29%2F3 = 20
Multiply by 3
p + q + r = 60
:
Subtract the 1st equation from the above equation
p + q + r = 60
p + q + 0 = 40
--------------------subtraction eliminates p & q
r = 20 age now
:
how old will r be after 10 years? r = 30