Question

The average (arithmetic mean) of k scores

is 20. The average of 10 of these scores
is 15. Find the average of the remaining
scores in terms of k.
(A) 20k +150/10
(B) 20k -150/10
(C) 150-20k/10
(D) 150 - 20k/k-10
(E) 20k -150/k-10

Answer 1

(E) (20k - 150)/(k - 10)

Explanation:

Sum of all scores = average × number of scores = 20 × k = 20k

Sum of 10 scores = 15 × 10 =150

Sum of remaining scores = 20k - 150

Number of remaining scores = k -10

Average of remaining scores = sum of remaining/no. remaining

= (20 k -150)/(k-10)