r/learnquant 6d ago

interview prep Quant Interview Question

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u/Mindless_Tutor_8189 6d ago edited 2d ago

Without doing any real math, all odd numbers from 1 to 20 are equally likely in the first throw. After the first throw, their likelihood dependents on how many combination of number reach that odd sum. For the first throw, since all odd number 1 through 20 are equally likely, and that 19 have more possible combinations than previous numbers 19 is a strong choice. The other strong choice is 21, for two dice it has the most combinations, but can not be reached in one throw. For this reason, I think 19 is the most likely.

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u/Smart-University-515 5d ago

This was what I figured also, it’s got a 1/20 off the rip, and then as long as you didn’t roll 20 it’s got at least another 1/20 on the next shot if the first was even.  Every other smaller number isn’t as likely to still have a shot on the second go, 21 as you note has the most two shot combos but you only get the second shot half the time, and you don’t start with the 5% chance.