Tuesday, August 27, 2019

What is Bob's number?....


ICYMI, I loved this logic riddle that Brilliant.org tweeted out last weekend — it’s a take-off of earlier similar puzzles in this genre (I've very slightly modified):

Alice and Bob are both logical and truthful, and each has complete knowledge that the other is logical and truthful. They are each given a distinct one-digit positive number in secret, and then they make these statements in the order given:

Alice: I don’t know who’s number is bigger.
Bob: I don’t know who’s number is bigger.
Alice: I still don’t know who’s number is bigger.
Bob: I still don’t know who’s number is bigger.
Alice: Now I know Bob’s number!

What is Bob’s number?

the answer is below; if you need further explanation go visit the comments to the original tweet here:
https://twitter.com/brilliantorg/status/1164885101148139521


....And as a bonus here's a problem Presh Talwalkar posted about yesterday that apparently went viral in India (it's a take-off on some older similar math riddles you may well be familiar with):
https://mindyourdecisions.com/blog/2019/08/26/worlds-toughest-riddle-explained/
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 answer:  Bob's number is 5




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