Three people

Three people - Peter, Quinton and Roland. 5 years ago, the average age of P and Q was 15 years. Present average age of P, Q and R is 20 years. Find the age of R after 10 years.

Correct answer:

R₂ =  30

Step-by-step explanation:

$$\begin{gathered} 15=\frac{(P-5)+(Q-5)}{2} \\ 20=\frac{P+Q+R}{3} \\ 30=P-5+Q-5 \\ 60=P+Q+R \\ 30=P+Q-10 \\ 60=P+Q+R \\ 40=P+Q \\ 60=P+Q+R \\ 60=40+R \\ R=60-40=20 \\ {R}_2=10+R=10+20=30 \end{gathered}$$

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