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Lets say there is 40% chance that an event will happen. Than it is said that the probability of the event is increased by five times. I do realize that the resulting percentage is not 200% or even 100%.

I do however assume, that the result will be 1 - (1 - 40%) / 5 = 88% (instead of increasing the probability, I decrease the opposite).

Now, is that correct? If not, what formula will calculate the new chance of the event depending on the probability multiplication?

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I think you're trying to extract a precise meaning from wild hyperbole. Don't waste your time. – dfeuer Dec 12 '13 at 7:32
I think you'll have to define "increasing the probability by five times" rigorously first before proceeding with your investigation. – Lost Dec 12 '13 at 7:55
can it be $45\%$? – the_candyman Dec 12 '13 at 9:29
@Lost I do not very strong in math, however I'll try: by another meaning, the chance of that the event will happen is five times more likely than before. – AgentFire Dec 12 '13 at 12:48
This is similar to this question – robjohn Dec 12 '13 at 12:57
up vote 1 down vote accepted

Using the reasoning in this answer, we get the odds to be $2/3:1$ and $5\times2/3=10/3$. The probability of an event with odds of $10/3:1$ is $10/13=76.923\%$

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