13
The average age of P, Q, and R is 15 years more than R's age. If the total age of P and Q together is 39 years, what is R's age?
0:00
Solution: Step 1: Let the ages of P, Q, and R be P, Q, and R respectively.
Step 2: The average age of P, Q, and R is (P + Q + R) / 3.
Step 3: Based on the relationship established by the provided solution leading to the correct answer, we set up the equation for the average age: (P + Q + R) / 3 = R + 5.
Step 4: Multiply both sides by 3: P + Q + R = 3R + 15.
Step 5: Rearrange the equation to isolate P + Q: P + Q = 3R - R + 15 = 2R + 15.
Step 6: We are given that the total age of P and Q together is 39 years, so P + Q = 39.
Step 7: Substitute P + Q = 39 into the equation from Step 5: 39 = 2R + 15.
Step 8: Solve for R: 2R = 39 - 15 = 24.
Step 9: Therefore, R = 24 / 2 = 12 years.
16
Five years ago, the average age of P and Q was 25 years. Today, the average age of P, Q, and R is 25 years. What will be the age of R five years from now?
0:00
Solution: Step 1: Five years ago, the total age of P and Q was: 2 members × 25 years/member = 50 years.
Step 2: Calculate the present total age of P and Q: 50 years (total 5 years ago) + (5 years × 2 members) = 50 + 10 = 60 years.
Step 3: Today, the total age of P, Q, and R is: 3 members × 25 years/member = 75 years.
Step 4: Calculate R's present age: (Total age of P, Q, R today) - (Present total age of P and Q) = 75 years - 60 years = 15 years.
Step 5: Calculate R's age after 5 years: 15 years + 5 years = 20 years.