Multiple choice

The average height of $10$ students in a class is $105\ cms$. If $20$ more students with an average height of $120\ cms$ join them what will be the average height be?

  1. $105\ cms$
  2. $110\ cms$
  3. $112\ cms$
  4. $115\ cms$
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D Correct answer
Explanation

Total height = (10 * 105) + (20 * 120) = 1050 + 2400 = 3450. Total students = 30. Average = 3450 / 30 = 115.

AI explanation

The total height of the initial 10 students is 10 times 105, which equals 1050 cms, and the total height of the 20 new students is 20 times 120, which equals 2400 cms. The combined total height for all 30 students is 1050 plus 2400, yielding 3450 cms. Dividing this combined total by 30 gives the new average height of 115 cms.

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