SOLUTION: Five years ago , the average 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 982628: Five years ago , the average 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):
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Five years ago , the average 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
:
Two equations
:
" Five years ago , the average of P and Q was 15 years"
%28%28p-5%29+%2B+%28q-5%29%29%2F2 = 15
multiply both sides 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
Find r
replace p + q with 40
40 + r = 60
r = 20 yrs old now
"how old will R be after 10 years"
r will be 30 yrs old