Average age of 4 family members of a family is 15 years. The average age of that family before the birth of their 3 years old twin kids was:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 24 years
Before the twins were born, the family had only the two parents, and that was 3 years ago, so the parents were 3 years younger each.
Total age of the 4 members now \(=4\times15=60\) years
Twins’ ages \(=3+3=6\) years, so the parents now \(=60-6=54\) years
Parents 3 years ago \(=54-2\times3=48\) years
Average then \(=48\div2=24\) years
Tip: Both parents were 3 years younger then. Forgetting this gives \(54\div2=27\), which is Option (3).