Shouldn’t we also calculate the number of ways of getting 90% and add? The result is 10/1024 and the final probability of a single student getting a C is 176/1024. This doesn’t really affect the final answer much, but I got ~53% as the final.
Why the 90%
And how is 176/1024 53%?
Sorry, I was unclear initially. Below is my solution. 90% is a way of getting at least a C. In the video it seems like only 70%, 80%, and 100% were considered as ‘at least a C.’
There are 10 ways to get 90%, so the probability is 10/1024. Therefore, the probability of getting at least a C is 176/1024. Hence, probability of not getting at least a C is (1024-176)/1024 which is ~0.83.
The probability of at least 1 student getting a C is 1 - P(no student getting a C) which is equal to 1 - (0.83)^4 which is approximately 53%.
Yep, your working is correct.
It should be 53%
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Indeed, and we’ve noted this in the video with thanks to the OP for catching the error.
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