Anonymous
Anonymous asked in Science & MathematicsMathematics · 5 years ago

 How many numbers are there?

from 1 to 10000,

exclude numbers which have 4 or 9.

How many numbers are there ?

6 Answers

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  • Joe
    Lv 5
    5 years ago
    Favorite Answer

    The number is 4096

    The best way to think of this one is to progressively remove the uncounted numbers.

    we start with 10000, and we know all 4000's and 9000's have to be removed.

    Each 10000 is 10% of the total so we remove 20% of the numbers ...

    down to 8000.

    Now with the stuff left we have to remove all the 400's and 900's

    that is also 20% that is 1600..etc , do that for the 10's and 1's and you end up with 4096

    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

    START 10000

    remove thousands 2000 8000

    remove hundreds 1600 6400

    remove tens 1280 5120

    remove ones 1024 4096

  • Anonymous
    5 years ago

    It's easier if you look at allowing leading zeros. That doesn't change the value of the number, but makes counting them easier.

    Start with 4-digit numbers. Each digit has 8 possibilities, so there are 8^4 = 2^12 = 4096 numbers.

    You have to toss out 0000 since that's too low. Then you add 10000 since that's 5 digits. You end up with the same number 4096.

    4096 is the answer.

  • Nick
    Lv 6
    5 years ago

    Numbers up to 9999 that don't have 4 or 9 = 8^4 = 4096

    add 1 for 10000 which had neither:

    4097 <----

  • sepia
    Lv 7
    5 years ago

    Exactly 8000

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  • 5 years ago

    about 8000

  • 5 years ago

    There are two options for the ten-thousand position, 1 and 0. That the zero just disappears doe not matter.

    For the other four digits, eight options:

    2 * 8^4, = 2^13 = 8192

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