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  4. How do I generate a number divisable by 5, and check it?

How do I generate a number divisable by 5, and check it?

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  • R riced

    Look at what I said - add 5 or 10. If a number is divisible by 5 it must end in 5 or 0 - that's primary school arithmetic. If you don't believe me write out the 5 times table for the numbers 1 to 20.

    Regards David R --------------------------------------------------------------- "Every program eventually becomes rococo, and then rubble." - Alan Perlis The only valid measurement of code quality: WTFs/minute.

    S Offline
    S Offline
    stephen darling
    wrote on last edited by
    #12

    riced wrote:

    If a number is divisible by 5 it must end in 5 or 0

    Yes; I was getting confused with the coding issue not the actual math.

    riced wrote:

    that's primary school arithmetic.

    I know, I am a Biomedical Scientist.

    riced wrote:

    If you don't believe me write out the 5 times table for the numbers 1 to 20.

    I do believe you. Like I said, it was the coding side of things. However, it is my fault the way I explained myself, it did indeed look as though I didn’t understand the math itself, and I certainly was not questioning you answer. Sorry if it came across that way, and thank you. Kind Regards, Stephen

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    • L Luc Pattyn

      David1987 wrote:

      except zero

      :confused::confused::confused:

      Luc Pattyn [My Articles] Nil Volentibus Arduum

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      David1987
      wrote on last edited by
      #13

      It depends on the definition of divisibility that you use. Zero can also be divisible by anything, if you use an other definition.

      L 1 Reply Last reply
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      • R riced

        Generate a four digit random number, multiply it by 10, add 5 (or 10). The result will be divisible by 5.

        Regards David R --------------------------------------------------------------- "Every program eventually becomes rococo, and then rubble." - Alan Perlis The only valid measurement of code quality: WTFs/minute.

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        Simon Bang Terkildsen
        wrote on last edited by
        #14

        you shouldn't add 5 or 10 but 5 or 0. In the case the random generator provides 9999 then you would get 9999 * 10 + 10 = 99990 + 10 = 100000 six digits

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        • D David1987

          It depends on the definition of divisibility that you use. Zero can also be divisible by anything, if you use an other definition.

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          Luc Pattyn
          wrote on last edited by
          #15

          BS.

          zero times x equals zero, no matter what (finite) value x has.

          so (the right side's) zero is divisible by x, and the result is (the left side's) zero. If I hold 10 pies, 5 bacon sandwiches, and zero glasses of milk, I have no problem distributing them evenly to 5 people. Next you'll state you could also redefine 5, so it no longer divides itself. :)

          Luc Pattyn [My Articles] Nil Volentibus Arduum

          OriginalGriffO D 2 Replies Last reply
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          • L Luc Pattyn

            BS.

            zero times x equals zero, no matter what (finite) value x has.

            so (the right side's) zero is divisible by x, and the result is (the left side's) zero. If I hold 10 pies, 5 bacon sandwiches, and zero glasses of milk, I have no problem distributing them evenly to 5 people. Next you'll state you could also redefine 5, so it no longer divides itself. :)

            Luc Pattyn [My Articles] Nil Volentibus Arduum

            OriginalGriffO Offline
            OriginalGriffO Offline
            OriginalGriff
            wrote on last edited by
            #16

            Luc Pattyn wrote:

            Next you'll state you could also redefine 5, so it no longer divides itself.

            It doesn't. There are only four bacon sandwiches left... :laugh:

            Real men don't use instructions. They are only the manufacturers opinion on how to put the thing together. Manfred R. Bihy: "Looks as if OP is learning resistant."

            "I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
            "Common sense is so rare these days, it should be classified as a super power" - Random T-shirt

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            • L Luc Pattyn

              BS.

              zero times x equals zero, no matter what (finite) value x has.

              so (the right side's) zero is divisible by x, and the result is (the left side's) zero. If I hold 10 pies, 5 bacon sandwiches, and zero glasses of milk, I have no problem distributing them evenly to 5 people. Next you'll state you could also redefine 5, so it no longer divides itself. :)

              Luc Pattyn [My Articles] Nil Volentibus Arduum

              D Offline
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              David1987
              wrote on last edited by
              #17

              Nope. You seem to think that that is the only definition of divisibility. I did not personally redefine anything. There is no natural number n such that 0/x=n so no x evenly divides 0. If you use the definition with integers instead of natural numbers, everything divides zero. Also, the prime factorization of zero is empty.

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              • S stephen darling

                Hi. First, how would I create a random number, and then add the last digit, so that it is divisable by 5? the number should always be 5 digits long. Second, how do I check it, I think I need to do something like...

                if (int x MOD 5 ==0)

                Or something like that. The first step is the most important though. Thank you, Steve

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                Lost User
                wrote on last edited by
                #18

                Didn't you already post this in the Q&A and get an answer to it?? Generating numbers to the multiple of 5?[^]

                Computers have been intelligent for a long time now. It just so happens that the program writers are about as effective as a room full of monkeys trying to crank out a copy of Hamlet.

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                • D David1987

                  Nope. You seem to think that that is the only definition of divisibility. I did not personally redefine anything. There is no natural number n such that 0/x=n so no x evenly divides 0. If you use the definition with integers instead of natural numbers, everything divides zero. Also, the prime factorization of zero is empty.

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                  Luc Pattyn
                  wrote on last edited by
                  #19

                  natural numbers are the ordinary counting numbers 1, 2, 3, ... (sometimes zero is also included) is what Wikipedia[^] offers as a definition. Now you can choose: either you include zero and you are allowed to use it at both sides of your 0/x=n, or you exclude it (and then your "except zero" remark that started all this is completely irrelevant). :doh:

                  Luc Pattyn [My Articles] Nil Volentibus Arduum

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                  • OriginalGriffO OriginalGriff

                    Luc Pattyn wrote:

                    Next you'll state you could also redefine 5, so it no longer divides itself.

                    It doesn't. There are only four bacon sandwiches left... :laugh:

                    Real men don't use instructions. They are only the manufacturers opinion on how to put the thing together. Manfred R. Bihy: "Looks as if OP is learning resistant."

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                    L Offline
                    Luc Pattyn
                    wrote on last edited by
                    #20

                    Sorry for the late reply, I have been off-line this evening, I have another tournament going on this week. I trust all bacon sandwiches have magically disappeared by now, and so the problem got solved? :)

                    Luc Pattyn [My Articles] Nil Volentibus Arduum

                    1 Reply Last reply
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                    • S stephen darling

                      riced wrote:

                      If a number is divisible by 5 it must end in 5 or 0

                      Yes; I was getting confused with the coding issue not the actual math.

                      riced wrote:

                      that's primary school arithmetic.

                      I know, I am a Biomedical Scientist.

                      riced wrote:

                      If you don't believe me write out the 5 times table for the numbers 1 to 20.

                      I do believe you. Like I said, it was the coding side of things. However, it is my fault the way I explained myself, it did indeed look as though I didn’t understand the math itself, and I certainly was not questioning you answer. Sorry if it came across that way, and thank you. Kind Regards, Stephen

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                      Mycroft Holmes
                      wrote on last edited by
                      #21

                      Your confusion did lead me to think - how old is this guy, doesn't understand primary grade maths :-D

                      Never underestimate the power of human stupidity RAH

                      1 Reply Last reply
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                      • L Luc Pattyn

                        natural numbers are the ordinary counting numbers 1, 2, 3, ... (sometimes zero is also included) is what Wikipedia[^] offers as a definition. Now you can choose: either you include zero and you are allowed to use it at both sides of your 0/x=n, or you exclude it (and then your "except zero" remark that started all this is completely irrelevant). :doh:

                        Luc Pattyn [My Articles] Nil Volentibus Arduum

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                        D Offline
                        David1987
                        wrote on last edited by
                        #22

                        Yes but that's precisely the point, you can choose.

                        1 Reply Last reply
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                        • D David1987

                          Generate a random integer in [2000, 19999] and multiply it by 5. The result will always be in [10000, 99999] (ie 5 decimal digits) and be divisible by 5 (by construction)

                          int yourNumber = 5 * rand.Next(2000, 20000); // remember the max-bound is exclusive
                          if (yourNumber % 5 != 0)
                          Console.WriteLine("the universe is wrong");

                          And make sure you reuse a single instance of Random, if you create new ones the result won't be random. [/spoon feeding]

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                          stephen darling
                          wrote on last edited by
                          #23

                          David1987 wrote:

                          And make sure you reuse a single instance of Random,

                          How exactly do I ensure that I am doing this? I am using rand a number of times, and although I get different values, it does appear that they are very simular. Regards, Stephen

                          1 Reply Last reply
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                          • D David1987

                            Nope. You seem to think that that is the only definition of divisibility. I did not personally redefine anything. There is no natural number n such that 0/x=n so no x evenly divides 0. If you use the definition with integers instead of natural numbers, everything divides zero. Also, the prime factorization of zero is empty.

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                            B Offline
                            BobJanova
                            wrote on last edited by
                            #24

                            That is a stupid definition. It would also indicate that -10 is not divisible by 5. There may be abstruse mathematical concepts for which it's useful, I suppose, but for normal maths it is nonsense.

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                            • S stephen darling

                              Does this mean that no matter what number I generate, it will always have to end in 5? e.g. All these numbers are divisable by 5

                              39485
                              99045
                              12095
                              49385
                              99335

                              However, I was under the impression I could generate numbers that would be divisable by 5, but not end in 5? Is this wrong? Regards, Stephen

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                              Gary Wheeler
                              wrote on last edited by
                              #25

                              All integers evenly divisible by 5 must end in either 5 or 0 when expressed in base 10. This is basic math.

                              Software Zen: delete this;

                              1 Reply Last reply
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                              • S stephen darling

                                Hi. First, how would I create a random number, and then add the last digit, so that it is divisable by 5? the number should always be 5 digits long. Second, how do I check it, I think I need to do something like...

                                if (int x MOD 5 ==0)

                                Or something like that. The first step is the most important though. Thank you, Steve

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                                T Offline
                                Tom Chantler
                                wrote on last edited by
                                #26

                                Is this a joke question? Generate a four digit number and add an extra number to the end, being either 5 or 0. Then don't check it because it will be correct!!! e.g. 4678; add 5 on the end to give 46785.

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                                • S stephen darling

                                  Hi. First, how would I create a random number, and then add the last digit, so that it is divisable by 5? the number should always be 5 digits long. Second, how do I check it, I think I need to do something like...

                                  if (int x MOD 5 ==0)

                                  Or something like that. The first step is the most important though. Thank you, Steve

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                                  Paulo_JCG
                                  wrote on last edited by
                                  #27

                                  Random random = new Random(); return (random.Next(17999) + 2000) * 5; this gives a number divisable by 5 between 10000 and 99995

                                  Paulo Gomes Over and Out :D

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                                  • S stephen darling

                                    riced wrote:

                                    If a number is divisible by 5 it must end in 5 or 0

                                    Yes; I was getting confused with the coding issue not the actual math.

                                    riced wrote:

                                    that's primary school arithmetic.

                                    I know, I am a Biomedical Scientist.

                                    riced wrote:

                                    If you don't believe me write out the 5 times table for the numbers 1 to 20.

                                    I do believe you. Like I said, it was the coding side of things. However, it is my fault the way I explained myself, it did indeed look as though I didn’t understand the math itself, and I certainly was not questioning you answer. Sorry if it came across that way, and thank you. Kind Regards, Stephen

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                                    M Offline
                                    mmwlada
                                    wrote on last edited by
                                    #28

                                    stephen.darling wrote:

                                    riced wrote:

                                    that's primary school arithmetic.

                                    I know, I am a Biomedical Scientist.

                                    You are NOT a scientist. A scinetist knows elementary math. You should be ashamed of yourself.

                                    There can be only one.

                                    S R N 3 Replies Last reply
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                                    • M mmwlada

                                      stephen.darling wrote:

                                      riced wrote:

                                      that's primary school arithmetic.

                                      I know, I am a Biomedical Scientist.

                                      You are NOT a scientist. A scinetist knows elementary math. You should be ashamed of yourself.

                                      There can be only one.

                                      S Offline
                                      S Offline
                                      stephen darling
                                      wrote on last edited by
                                      #29

                                      mmwlada wrote:

                                      You are NOT a scientist. A scinetist knows elementary math. You should be ashamed of yourself.

                                      How dare you! I may be a beginner in the programming world, but to be spoken to in this way from someone who does not know me is extremely rude! I am indeed a scientist, registered in the UK as a practising biomedical scientist, not that I need to explain myself to you! As for the math, if you took the time to read through the post, you would see that I simply explained myself wrong, and it was the programming that I was struggling with, and not the math. As for being ashamed of myself; I do not know what your problem is, but believe me, I have nothing to be ashamed of, and could now go on to say allot about, and to you, however, I will refrain! Stephen

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                                      • S stephen darling

                                        riced wrote:

                                        If a number is divisible by 5 it must end in 5 or 0

                                        Yes; I was getting confused with the coding issue not the actual math.

                                        riced wrote:

                                        that's primary school arithmetic.

                                        I know, I am a Biomedical Scientist.

                                        riced wrote:

                                        If you don't believe me write out the 5 times table for the numbers 1 to 20.

                                        I do believe you. Like I said, it was the coding side of things. However, it is my fault the way I explained myself, it did indeed look as though I didn’t understand the math itself, and I certainly was not questioning you answer. Sorry if it came across that way, and thank you. Kind Regards, Stephen

                                        F Offline
                                        F Offline
                                        FunkySteve
                                        wrote on last edited by
                                        #30

                                        Actually, every number is divisible by 5.

                                        S 1 Reply Last reply
                                        0
                                        • F FunkySteve

                                          Actually, every number is divisible by 5.

                                          S Offline
                                          S Offline
                                          stephen darling
                                          wrote on last edited by
                                          #31

                                          FunkySteve wrote:

                                          Actually, every number is divisible by 5

                                          True. Again, my fault for not explaining properly. I meant a modulus of zero, so that 13285 MOD 5 = 0 Got it all sorted now, thanx to most people, disregarding one perticular ignorant comment :confused: Thank you, Steve

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