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Voltmeter

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Voltmeter

by anuptvm » Wed Dec 29, 2010 6:23 am
A certain meter can record voltages between 0 and 10 (both inclusive). If the average of 3 readings is 8 volts, what was the smallest possible recording, in volts?

A. 2 B. 3 C. 4 D. 5 E. 6

My answer was 6 which is wrong.
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by anshumishra » Wed Dec 29, 2010 6:32 am
anuptvm wrote:A certain meter can record voltages between 0 and 10 (both inclusive). If the average of 3 readings is 8 volts, what was the smallest possible recording, in volts?

A. 2 B. 3 C. 4 D. 5 E. 6

My answer was 6 which is wrong.
(a+b+c)/3 = 8
=> a+b+c = 24
We want to minimize a, lets maximize b and c (which is 10)

=> a = 24 - 2*10 = 4.
OA is C.
Thanks
Anshu

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by Anurag@Gurome » Wed Dec 29, 2010 6:44 am
anuptvm wrote:A certain meter can record voltages between 0 and 10 (both inclusive). If the average of 3 readings is 8 volts, what was the smallest possible recording, in volts?

A. 2 B. 3 C. 4 D. 5 E. 6
Sum of the three readings = 3*8 = 24

Now to make one of the reading smallest we have to maximize the other two as their sum is constant. Now maximum possible value of the other two reading is 10.

Therefore, smallest possible reading = 24 - 2*10 = 4

The correct answer is C.
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