Answer:
Explanation:
Let the sum of the original list of n numbers be S. The average of the list is given by:
average = S/n
Since the average is 90, we can write:
90 = S/n
Multiplying both sides by n, we get:
90n = S
After the number 90n is added to the list, the average of the list becomes 168. The sum of the list is now S + 90n. The number of elements in the list is now n+1. The average of the list is given by:
average = (S + 90n) / (n+1)
Since the average is 168, we can write:
168 = (S + 90n) / (n+1)
Multiplying both sides by n+1, we get:
168(n+1) = S + 90n
Substituting for S using the equation S = 90n, we get:
168(n+1) = 90n + 90n
Simplifying, we get:
168n + 168 = 180n
Subtracting 168n from both sides, we get:
168 = 12n
Dividing both sides by 12, we get:
14 = n
Therefore, n = 14.