Anonymous
Anonymous asked in Science & MathematicsMathematics · 9 years ago

If you count down from 1 to 100, how many number 5s will you pass on the way?

this question probably sounds basic or stupid.. however im doing a little research..

the answer to this question is 12. and I think the numbers would be

5, 15, 25, 35, 45, 50, 55, 65, 75, 85, 95 (55 counted as 2)

this would give a total of 12. would you agree?

I hear some people saying to include 51, 52, 53 etc.

Thanks.

Update:

sorry i meant if you count FROM 1 to 100. Not count down.

Update 2:

AND THE ANSWER IS 12. i just want to know how its 12.

5 Answers

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  • M3
    Lv 7
    9 years ago
    Favorite Answer

    you DO have to count 51, 52 etc

    and you can compute the total in a much simpler way thus:

    change the q to counting from 00 to 99 (it doesn't change # of 5's)

    in each of the 2 columns, 1/10 of the 100 digits will be 5, so

    2 *1/10 *100 = 20 <--------------

    your AD

    ======

    if the ans is 12, the q has to be # of 5's IN MULTIPLES OF 5 from 1 to 100

  • tommi
    Lv 4
    4 years ago

    Count 1 To 100

  • Pranil
    Lv 7
    9 years ago

    From 1 to 100

    0 is repeated for 11 times

    1 is repeated for 21 times

    3 to 9 repeats for 20 times

    so there are 20 numbers that contain 5 in it

    5, 15, 25, 35, 45, 50, 51 to 59, 65, 75, 85, 95

    (55 contains 2 five's)

    -------

  • 9 years ago

    None, because you cant count down from 1 to reach 100. You have to count up.

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  • Anonymous
    9 years ago

    None of the above

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