The average of 13 numbers is 75. If the average of the first six is 70 and the average of the last six is 80, find the 7th number.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 75
Sum of 13 numbers = 13 × 75 = 975
Sum of first 6 numbers = 6 × 70 = 420
Sum of last 6 numbers = 6 × 80 = 480
Seventh number = 975 - (420 + 480)
⇒ 975 - 900 = 75