Let k=number of 4's to add
then
E(x)=Σx*P(x)
=(8*2+(2+k)*4)/(8+2+k)
If E(x)≥3.5
then
(8*2+(2+k)*4)/(8+2+k)≥3.5
solve by cross multiplication
16+8+4k≥35+3.5k
0.5k≥11
k≥22
Suppose I 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 I have to add before the expected value is at least 3.5?
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6 answers