The average of 33 numbers is 70. The average of the first 17 numbers is 65, and the average of the 17 numbers is 74. If the 17th number is excluded, what is the average of the remaining numbers (approximate to one decimal place)?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 70.5.
Total sum of 33 numbers = 33 × 70 = 2310
Sum of first 17 numbers = 17 × 65 = 1105
Sum of last 17 numbers = 17 × 74 = 1258
17th number = 1105 + 1258 - 2310 = 53
Exclude the 17th number: New sum = 2310 - 53 = 2257
New average = 2257/32 ≈ 70.5