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Math Help - mathematical operations

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    Question mathematical operations

    how it is possible to remove the last three-digit of a number N using two mathematical operations
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  2. #2
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    Quote Originally Posted by hebby View Post
    how it is possible to remove the last three-digit of a number N using two mathematical operations
    \left\lfloor {\frac{N}{{1000}}} \right\rfloor ???
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    Quote Originally Posted by hebby View Post
    how it is possible to remove the last three-digit of a number N using two mathematical operations

    What kind of number is N? What three "last digits": from the right or from the left? What do you mean by "removing digits"?? What mathematical operations are allowed: sum, multiplication, power, taking logarithms...??
    Common, some definitions!

    Tonio
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    well that well only get u a decimal with all the digits still there
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    ya basically from the right....ie the last 3 digits....the operations u mentioned are all valid.....but a general method...to remove the last 3 digits from any number N
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    N= whole number...integer
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    eg) 12345=N and u end up getting 12....but minus last 3 divide by 100 is not valid as this can be applied once we know the numbers....but we actually dont know the number N
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    Quote Originally Posted by hebby View Post
    ya basically from the right....ie the last 3 digits....the operations u mentioned are all valid.....but a general method...to remove the last 3 digits from any number N

    No operations needed: if the number is N=a_1a_2\ldots a_n\,,\,\,a_i\in\{0,1,2,\ldots,9\} , then take N'=a_1\ldots a_{n-3}

    Or more seriously: take \left[\frac{N}{1000}\right], as already proposed by Plato.

    Tonio
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    hey thanks, but how would the N divided by 1000 work? as you will end up with a number with decimals, how would you remove those?
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    Quote Originally Posted by hebby View Post
    hey thanks, but how would the N divided by 1000 work? as you will end up with a number with decimals, how would you remove those?
    Do you understand the floor function (greatest integer function)?
    \frac{{6346765}}{{1000}} = 6346.765\,\text{ so } \,\left\lfloor {\frac{{6346765}}{{1000}}} \right\rfloor  = 6346
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    no i never saw that before, but i can see how that would work now
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  12. #12
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    Hi

    I was think in the lines of

    1) Multiply by 10^ -3

    2) The we end up with a decimal, how can I remove the decimal from the integer?

    Any ideas?
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    I was thinking ... would the floor function be considered as an operation? Just curious about that

    Could you also try ( N - ( N (mod 1000) ) ) / 1000? Basically, N minus the remainder when you divide by 1000, then divide that by 1000 ....
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    Could you show a numerical example on how that might work?
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    Quote Originally Posted by Bingk View Post
    I was thinking ... would the floor function be considered as an operation? Just curious about that

    Could you also try ( N - ( N (mod 1000) ) ) / 1000? Basically, N minus the remainder when you divide by 1000, then divide that by 1000 ....
    x-\{x\}=\lfloor x\rfloor . But, \frac{N}{1000}-N\text{ mod }1000=\frac{N}{1000}-\left\{\frac{N}{1000}\right\}=\left\lfloor \frac{N}{1000}\right\rfloor. So, really all you've done is restate Plato's response.
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