The average of six numbers is 20. If one number is removed, the average becomes 15. What is the number removed ?

Given that ,The average of six numbers = 20 ⇒ sum of six numbers = 6 × 20 = 120 The average of 5 numbers = 15 ⇒ sum of six numbers = 5 × 5 = 75 ∴ Required number = sum of six numbers – sum of five numbers Required number = 120 – 75 = 45