The world's youngest parents were 8 and 9 years old, who lived in

The average age of a group of 4 friends is 36 years. The youngest friend amongst them is 6 years old. What was the average age of the group at the time of the birth of the youngest friend?

In a family of 5 members, the average age at present is 33 years. The youngest member is 9 years old. The average age of the family just before the birth of the youngest member was

The odds against a man who is 45 years old, living till he is 70 are 7:5 and the odds against his wife who is now 36, living till she is 61 are 5:3 . Find the probability that (a) the couple will be alive 25 years hence, (b) at least one of then will be alive 25 years hence.

The odds against a husband who is 60 years old, living till he is 85 are 7:5 . The odds against his wife who is now 56, living till she is 81 are 5:3 . Find the probabilty that: at least one of them will be alive 25 years hence.