Multiple choice

The average of k numbers is 20, and the average of 10 of these numbers is 10. In terms of k, find the average of the remaining numbers.

  1. 10

  2. 20k

  3. (20k - 100)/10

  4. 20(k - 5)/(k - 10)

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

Sum of k numbers = 20k. Sum of 10 numbers = 10 * 10 = 100. Sum of remaining (k-10) numbers = 20k - 100. Average of remaining = (20k - 100) / (k - 10) = 20(k - 5) / (k - 10).

AI explanation

Using the formula sum = average * count, the sum of all k numbers is 20k, and the sum of the 10 numbers is 10 * 10 = 100. The sum of the remaining (k - 10) numbers is therefore 20k - 100. Divide this remaining sum by the number of remaining terms, (k - 10), to find the new average: (20k - 100) / (k - 10). Factoring out a 20 from the numerator gives the final expression of 20(k - 5) / (k - 10).

Keep practicing — related questions