• M0

    For the mini challange at the end of the video, is there any other cool or quick way to get 210. Because I got all the 14 bad numbers. I listed them systamatically and it was correct but didn't consisted 210. So how to catch these tiny numbers hidden if you don't have any idea and believe on your listing?

  • ADMIN M0★ M1 M5

    @fabulousgrizzly I suppose one way is to just be watchful of this one tricky area, which comes up a lot in these sorts of questions! Whenever you see questions like,

    • "How many 3-digit numbers can you make with the digits ___...?"

    • "How many numbers have digits that are consecutive..?"

    • "How many 2-digit numbers do not contain the digit 0...?"

    • "What is the probability that a random 3-digit number has a zero as a digit...?"

    ...then after awhile (maybe after making some mistakes along the way!), you learn to be prepared to watch for the tricky zero digits. A number can't start with 0. It's something good to keep in the back of your head! 🙂