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Source: — Problem Solving |

Re: average

by dtweah » Sat May 16, 2009 3:02 pm
shibal wrote:If the avg of 5 positive temperatures is x degrees Fahrenheit, then the sum of the 3 greatest of these temperatures, in degress is?

OA: 4x
(1+2+3+4+5)/5=3

Sum of three largest is 12
4 x 3 =12 Succeeds.

But is this true in general?

(2 +3 +4 +5 +6)/5=4

Sum of 3 largest is 15
4 x 4 = 16 Fails.

Or is this only unique to the farenheit scale?

If (a +b +c +d +e)/5=x
(a +b +c +d +e) =5x

Let y= sum of largest 3
and z equal sum of smallest 2 numbers

z+y=5x

z +y = 4x +x

z+ y = 4x + (z+y)/5

I mean were are we going with this?
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