Question

1.The average of 9 numbers in a list is 6. What is the sum of these 9 numbers?

2.Then the number 26 is added to the list. What is the average of the 10 numbers in the new list?

Answer 1

(1) average  = sum / 9

6 = sum / 9

sum = 6*9 = 54

(2) new average = (sum + 26)/10 = (54+26)/10 = 8

new average is 8