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# solutions to combinatorics exercises

Your answer is wrong (to the problem of, how many 2-digit numbers have the digit of tens strictly smaller than the digit of units)

Note by Predrag Tosic
2 years, 11 months ago

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Yes, you are correct. 'My' question has the answer of 36, your question has the answer of 45. My recollection of the exact formulation was wrong (generally I work on these problems in my head, i.e.., without paper, pen or repeated looking on the screen -- so, it's probably bound to happen every now and then...)

- 2 years, 11 months ago

Do you have any feedback on your usage of Brilliant? Is there any thing that you would like us to improve on?

Staff - 2 years, 11 months ago

If you believe that a practice problem is wrong, you can report it directly and we will take a look at it.

I do not see a question of "how many 2-digit numbers have the digit of tens strictly smaller than the digit of units" in the practice section. The closest question that I see is "How many 2 digit numbers are there, such that the units digit is strictly smaller than the tens digit?". These 2 questions would have different answers.

Staff - 2 years, 11 months ago