Difference between revisions of "2022 MMATHS Individual Round Problems/Problem 4"

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Claire says, "Now I know your favorite number!" What is Cat's favorite number?
 
Claire says, "Now I know your favorite number!" What is Cat's favorite number?
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==Solution 1==

Revision as of 11:30, 19 December 2022

Problem

Cat and Claire are having a conversation about Cat's favorite number. Cat says, "My favorite number is a two-digit perfect square!"

Claire asks, "If I picked a digit of your favorite number at random and revealed it to me without telling me which place it was in, is there a chance I'd know for certain what it is?"

Cat says, "Yes!" Moreover, if I told you a number and identified it as the sum of the digits of my favorite number, or if I told you a number and identified it as the positive difference of the digits of my favorite number, you wouldn't know my favorite number!

Claire says, "Now I know your favorite number!" What is Cat's favorite number?

Solution 1