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On each of the first three days of January, there is a 1/2 chance that it will snow where Bob lives. On each of the next four days, there is a 1/3 chance that it will snow. What is the probability that it snows at least once during the first week of January?

 Jan 13, 2021
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We can use complementary counting for this problem by calculating the probability that it will not snow at all first.

That is equal to 

(12)3(23)4=181681=281

But we're trying to find the probability that it will snow at least once, so the answer is 1281=7981

Here's a very similar problem: https://web2.0calc.com/questions/please-help-complementry-probabilty-problem

 Jan 13, 2021

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