The average of 6 positive numbers is 10. If one number is excluded, the average becomes 9. What is the excluded number?
Show answer & explanation
Correct answer: A
Explanation
Number of items = 6
Average = 10
New number of items = 5
New average = 9
Initial sum = 6 × 10 = 60
New sum = 5 × 9 = 45
Removed number = 60 − 45 = 15