Multiple choice

The average age of a group of 10 students is 15 years. When 5 more students join the group, the average age increases by 1 year. The average age of the new students is?

  1. $45$
  2. $20$
  3. $18$
  4. $90$

  5. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Original total age = 10 × 15 = 150 years. New total = 15 × 16 = 240 years. Sum of new students' ages = 240 - 150 = 90 years. Average age of 5 new students = 90 ÷ 5 = 18 years. The average increases because the new students are older than the original average.

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