Multiple choice

The average age of a five member family is 20, if one member gone then average is equal to 15, what is the age of member, while was gone?

  1. $20$
  2. $30$
  3. $40$
  4. $50$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the member who left be age x. Total age of 5 members = 5×20 = 100. Total age of remaining 4 members = 4×15 = 60. So the member who left was 100-60 = 40 years old. This uses the basic average formula: Average = Sum/Count.

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