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Suppose we have a bag with 10 slips of paper in it. Eight of these have a 2 on them and the other two have a 4 on them.

How many 4's do we have to add to make the expected value equal to 3?

 Nov 25, 2018
 #1
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2 * [ 8 / (10 + x) ]   +  4  [  x + 2] / [10 + x]  =  3

 

Where x is the number of additional slips  showing "4"

Simplify the above.....and we get

 

[ 16 +  4x + 8 ] / [ 10 + x ]  = 3

 

24 + 4x      =  3 [ 10 + x ]

 

24 + 4x = 30 + 3x

 

x =  6

 

 

cool  cool  cool

 Nov 25, 2018
edited by CPhill  Nov 25, 2018

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