The average age of 6 members of a family is 25 years. If the youngest member of the family is 15 years old, then what was the average age (in years) of the family at the time of the birth of the youngest member?

The current total age of the 6 family members is 6 multiplied by 25, which equals 150 years. At the time of the youngest member's birth 15 years ago, the total age of the other 5 members was 150 minus 15 years of age reduction for each of the 6 members, which is 150 minus 90, equaling 60. The average age of the 5 members at that time was 60 divided by 5, which is 12 years. The result is B.

• Thanks
• Wrong explanation