Art of Problem Solving: Make a List

Art of Problem Solving's Richard Rusczyk solves problems by making lists.

[abishekthiyagarajan]

Why no square number end with 7? Because the unit digit of any number squared will not end in 7. Square numbers will also not end in 2, 3, 8.

[benrythefox]

All of the numbers in the second problem were even. That is because in a group of three consecutive numbers, there has to be at least one even number, and when you multiply a number by an even number, you get another even number.

[someperson]

10:30 I know I'm 9 years late but 24 also satisfies both those conditions

[alexknapp]

I love aops its the best I just finished the pre-algebra book

[brandonmonsen]

OR you could... CHINESE REMAINDER THEOREM! That saved my butt during math team this year since modular arithmetic was one of the topics.

[jangwoo]

Why do you try to disguise yourself as "the other guy" because the description clearly states that you are "Richard Rusczyk"

[nightterror]

this guy is crazy i think he escaped prison