Multiple choice

The average age of 4 boys is 20 years. A new boy joins them and their average age increases to 21 years. What is the age of the new boy?

  1. 22 years

  2. 23 years

  3. 24 years

  4. 25 years
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sum of ages of 4 boys = 4 * 20 = 80. Sum of ages of 5 boys = 5 * 21 = 105. Age of new boy = 105 - 80 = 25.

AI explanation

The total age of the 4 boys initially is 4 times 20 years, which equals 80 years. When the new boy joins, the total age of the 5 boys becomes 5 times 21 years, which equals 105 years. The age of the new boy is the difference between the new total and the old total, so 105 minus 80 equals 25 years.

Keep practicing — related questions