ACT Math · Statistics and data analysis
The mean of 6 numbers is 18. If one of the numbers is removed, the mean of the remaining 5 numbers is 20. What was the value of the number…
The mean of 6 numbers is 18. If one of the numbers is removed, the mean of the remaining 5 numbers is 20. What was the value of the number that was removed?
Answer and explanation
Answer: G: 8
The total of all 6 numbers is 18×6=108. The total of the remaining 5 numbers is 20×5=100. The removed number is 108−100=8. Choice F reverses the order of subtraction, computing 100−108=−8. Choice H comes from multiplying the difference in the two means by the new count instead of using full totals: (20−18)×5=10. Choice J simply reports the original mean without completing the calculation.
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