The mean of five numbers is 18. If a sixth number is added, the new mean becomes 20. What is the sixth number?
Answer and explanation
Correct answer: B. 30
- Step 1: Total of first 5 numbers = 5 18 = 90. Step 2. Total of all 6 numbers = 6 20 = 120. Sixth number = 120 - 90 = 30. Answer: 30. Why not the others: 24 adds the increase to the mean; 26 assumes sum was 94; 28 is an arithmetic subtraction error.
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