Multiple choice

The average age of the family of five members is 48. If the present age of the youngest member is 16 years, then what was the average age of the family in the past at the time just before the birth of the youngest member?

  1. 40 years

  2. 36 years

  3. 32 years

  4. 20 years
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Total age now = 5 * 48 = 240. 16 years ago, each of the 4 members (excluding the youngest) was 16 years younger. Total age then = 240 - (5 * 16) = 240 - 80 = 160. Average age of 4 members = 160 / 4 = 40.

AI explanation

The total sum of the present ages of the 5 family members is 5 * 48 = 240 years. Just before the birth of the 16-year-old youngest member, there were only 4 members in the family, and we must subtract the youngest member's age from the total sum, making the past sum 224 years. To find the average age of the family at that time, we must also subtract 16 years from the ages of the 4 older members, resulting in an age reduction of 4 * 16 = 64 years for the group. The total age of the 4 members at that past time was therefore 224 - 64 = 160 years, and dividing this by 4 yields an average age of 40 years.

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