suppose u place bet of 100 on your favorite winning team tonight.?

Question

if u win, u will end up with 500 and the 100 u bet. if u lose, u get nothing. how likely would victory ave to be to make placing the have positive expected value? 
50 percent
20 perent
larger than 20 percent

BigBadSteve · Answer

I bet you're a cheat and too lazy to even transpose a question correctly. I bet you fail maths this year.

Puzzling · Answer

Let's assume the probability of winning is p.

If you win (probability = p), you have a net gain of 500 (you get back the bet, so that doesn't count).
If you lose (probability = 1 - p), you have a net "gain" of -100.

So the expected value is:
E(X) = 500p + -100(1 - p)

You want that to be positive (aka > 0):
500p + -100(1 - p) > 0
500p - 100 + 100p > 0
600p - 100 > 0
600p > 100
p > 100/600
p > 1/6
p > 0.166666...

Answer:
At least 16⅔%

Pope · Answer

By expected value, you mean expectation of earnings for "u"? And those bet payoffs are in the same monetary unit? Let p be the probability of winning.

expectation > 0
500p - 100(1 - p) > 0

suppose u place bet of 100 on your favorite winning team tonight.?

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