oquiella wrote:The average of 6 numbers is 8.5, when one number is discarded, the average of the remaining numbers becomes 7.2. What is the discarded number.
A. 7.8
8. 9.8
C. 10
D. 12.4
E. 15.0
sum = (number)(average).
The average of 6 numbers is 8.5.
Sum of the 6 numbers = (6)(8.5) = 51.
When one number is discarded, the average of the remaining numbers becomes 7.2.
Sum of the remaining 5 numbers = (5)(7.2) = 36.
Discarded number = (sum of all 6 numbers) - (sum of the remaining 5 numbers) = 51-36 = 15.
The correct answer is
E.
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