Q1
The average age of three friends is 20 years and their ages are in the proportion 2:3:5, the age of the oldest friend is:
Answer: C
Asked: the age of the oldest friend.
Sum of the three ages = average × 3 = 20 × 3 = 60 years.
The ages are in the ratio 2 : 3 : 5, so let them be 2k, 3k and 5k.
2k + 3k + 5k = 10k = 60, so k = 6.
The oldest is 5k = 30 years. (The three ages are 12, 18 and 30. Their average is 20, which checks out.)
Answer: 30 years