Two years ago, the average age of a family of 8 members was 18 years.
Tech Mahindra technical mcq question, verified with a worked answer. Free to practise - no sign-up.
Two years ago, the average age of a family of 8 members was 18 years. After the birth of a baby, the average age of the family remains the same today. What is the present age of the baby?
Show answer & explanation
The total age of the original 8 members increases by 16 years over two years. Since the average age of the 9 members today is still 18, the total age must be 162. The difference between the current total and the updated total of the original members is the baby's age.
Step-by-step Derivation:
Step 1: Calculate the total age of the 8 members two years ago. Total age = 8 members * 18 years/member = 144 years.
Step 2: Calculate the total age of those same 8 members today. Since each person has aged 2 years, the total increase is 8 * 2 = 16 years. Current total for 8 members = 144 + 16 = 160 years.
Step 3: Determine the total age of the family today including the baby. There are now 9 members, and the average age is still 18. Total age = 9 members * 18 years/member = 162 years.
Step 4: Find the baby's age by subtracting the total age of the 8 members from the total age of the 9 members. Baby's age = 162 - 160 = 2 years.