UPCAT Mathematics practice question 8: The average of five numbers is 18. If one of them, 22, is removed, what is the average of the remaining four?
Correct answer
D. 17
The total is 5 × 18 = 90. Removing 22 leaves 68, and 68 ÷ 4 = 17.
The question
The average of five numbers is 18. If one of them, 22, is removed, what is the average of the remaining four?
- Option A: 16
- Option B: 18
- Option C: 19
- Option D: 17Correct
Why D is correct
The total is 5 × 18 = 90. Removing 22 leaves 68, and 68 ÷ 4 = 17.
Why the other options are wrong
- A 16
- Subtracts 22 from the total but then divides by 5 instead of the remaining 4.
- B 18
- Assumes removing a value leaves the mean unchanged. It only would if the removed value equalled the mean, and 22 is above 18.
- C 19
- Moves the average the wrong way. Removing a number larger than the mean must pull the mean down, not up.