Multiple choice

The average age of $4$ persons five years ago was $45$ years. By including a fifth person, the present average age of all the five is $49$ years. The present age of the fifth person is

  1. $64$ years
  2. $48$ years
  3. $45$ years
  4. $40$ years
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Sum of ages of 4 persons 5 years ago was 45 * 4 = 180. Their present sum is 180 + (4 * 5) = 200. With the 5th person, the present sum is 49 * 5 = 245. The 5th person's age is 245 - 200 = 45.

AI explanation

Five years ago, the average age of the 4 persons was 45 years, making their total age 4 times 45, or 180 years. Their present total age is therefore 180 plus 4 times 5, which equals 200 years. The present total age of all 5 persons is 5 times 49, or 245 years. The fifth person's present age is the difference between the two totals, 245 minus 200, which is 45 years.

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