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

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

Step-by-step 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)