The average of a set of 7 numbers is 18. If one number is removed, the average becomes 15. What is the value of the removed number?
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. 36.
Average = Sum of numbers/Number of terms
Let the sum of the 7 numbers = S7
The average of the 7 numbers = 18, so:
⇒ S7 = 18
⇒ S7 = 18 × 7 = 126
When one number is removed, the new average of the remaining 6 numbers is 15. Let the sum of the remaining 6 numbers be S6.
The average of the remaining numbers = 15
⇒ S6 = 15 × 6 = 90
⇒ Removed number = S7 − S6 = 126 − 90 = 36