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Math(s) problem - puzzle

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  • D dbrenth

    My teacher asked me to write a program on the board and solve it. I wrote:

    230 - 220 x 0.5

    and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.

    Brent

    D Offline
    D Offline
    Daniel Pfeffer
    wrote on last edited by
    #3

    You are wrong, the teacher is right. The order of precedence in mathematical operations is (mnemonic PEMDAS): Parentheses Exponentiation Multiplication & Division Addition & Subtraction If two operations have the same precedence, they are evaluated from left to right. Your problem may be rewritten as 230 - (220 x 0.5), the answer to which is obviously not 5.

    Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.

    K A M P D 7 Replies Last reply
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    • D dbrenth

      My teacher asked me to write a program on the board and solve it. I wrote:

      230 - 220 x 0.5

      and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.

      Brent

      Kornfeld Eliyahu PeterK Offline
      Kornfeld Eliyahu PeterK Offline
      Kornfeld Eliyahu Peter
      wrote on last edited by
      #4

      Have you write 5! as answer, or it is only for us as an expression of your frustration? :-)

      "The only place where Success comes before Work is in the dictionary." Vidal Sassoon, 1928 - 2012

      "It never ceases to amaze me that a spacecraft launched in 1977 can be fixed remotely from Earth." ― Brian Cox

      D 1 Reply Last reply
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      • Kornfeld Eliyahu PeterK Kornfeld Eliyahu Peter

        Have you write 5! as answer, or it is only for us as an expression of your frustration? :-)

        "The only place where Success comes before Work is in the dictionary." Vidal Sassoon, 1928 - 2012

        D Offline
        D Offline
        dbrenth
        wrote on last edited by
        #5

        See my hint to another responder.

        Brent

        1 Reply Last reply
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        • Richard Andrew x64R Richard Andrew x64

          Explain what to him? You are wrong.

          The difficult we do right away... ...the impossible takes slightly longer.

          D Offline
          D Offline
          dbrenth
          wrote on last edited by
          #6

          That's what he thought, too, until I actually said the answer out loud. Then he was quite embarassed. Obviously, this is a puzzle with a correct solution and not a real life experience.

          Brent

          Greg UtasG 1 Reply Last reply
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          • Greg UtasG Greg Utas

            You must have said "five factorial".

            Robust Services Core | Software Techniques for Lemmings | Articles
            The fox knows many things, but the hedgehog knows one big thing.

            D Offline
            D Offline
            dbrenth
            wrote on last edited by
            #7

            Ding ding ding.

            Brent

            D 1 Reply Last reply
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            • D dbrenth

              That's what he thought, too, until I actually said the answer out loud. Then he was quite embarassed. Obviously, this is a puzzle with a correct solution and not a real life experience.

              Brent

              Greg UtasG Offline
              Greg UtasG Offline
              Greg Utas
              wrote on last edited by
              #8

              You must have said "five factorial".

              Robust Services Core | Software Techniques for Lemmings | Articles
              The fox knows many things, but the hedgehog knows one big thing.

              <p><a href="https://github.com/GregUtas/robust-services-core/blob/master/README.md">Robust Services Core</a>
              <em>The fox knows many things, but the hedgehog knows one big thing.</em></p>

              D D 2 Replies Last reply
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              • Greg UtasG Greg Utas

                You must have said "five factorial".

                Robust Services Core | Software Techniques for Lemmings | Articles
                The fox knows many things, but the hedgehog knows one big thing.

                D Offline
                D Offline
                dandy72
                wrote on last edited by
                #9

                I thought about that...but who provides answers as a factorial?

                Greg UtasG C R 3 Replies Last reply
                0
                • D dbrenth

                  Ding ding ding.

                  Brent

                  D Offline
                  D Offline
                  Daniel Pfeffer
                  wrote on last edited by
                  #10

                  "5 factorial" is not a solution; it is simply representing the answer (120) as a different equation. If you were set a problem in a mathematics test 300 - 0.5 x 150 and answered that it is 450 / 2, the teacher would be justified in marking it incomplete because it has not been reduced to the simplest terms.

                  Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.

                  E 1 Reply Last reply
                  0
                  • D dbrenth

                    My teacher asked me to write a program on the board and solve it. I wrote:

                    230 - 220 x 0.5

                    and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.

                    Brent

                    S Offline
                    S Offline
                    SeeSharp2
                    wrote on last edited by
                    #11

                    dbrenth wrote:

                    the answer was 5!

                    five factorial. Unless you were yelling at them. :-D

                    1 Reply Last reply
                    0
                    • D dbrenth

                      My teacher asked me to write a program on the board and solve it. I wrote:

                      230 - 220 x 0.5

                      and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.

                      Brent

                      L Offline
                      L Offline
                      Lost User
                      wrote on last edited by
                      #12

                      dbrenth wrote:

                      Can you please explain it to him?

                      Dear Teacher, dbrenth is a cocky little so and so, who needs to be taken down a peg or two. ;P

                      O 1 Reply Last reply
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                      • D dandy72

                        I thought about that...but who provides answers as a factorial?

                        Greg UtasG Offline
                        Greg UtasG Offline
                        Greg Utas
                        wrote on last edited by
                        #13

                        I think it was meant as a riddle rather than something that actually happened.

                        Robust Services Core | Software Techniques for Lemmings | Articles
                        The fox knows many things, but the hedgehog knows one big thing.

                        <p><a href="https://github.com/GregUtas/robust-services-core/blob/master/README.md">Robust Services Core</a>
                        <em>The fox knows many things, but the hedgehog knows one big thing.</em></p>

                        D 1 Reply Last reply
                        0
                        • D dbrenth

                          My teacher asked me to write a program on the board and solve it. I wrote:

                          230 - 220 x 0.5

                          and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.

                          Brent

                          C Offline
                          C Offline
                          CPallini
                          wrote on last edited by
                          #14

                          You teacher was right, and told you the correct result was actually 76. Could you please tell us why?

                          "In testa che avete, Signor di Ceprano?" -- Rigoletto

                          F D 2 Replies Last reply
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                          • Greg UtasG Greg Utas

                            I think it was meant as a riddle rather than something that actually happened.

                            Robust Services Core | Software Techniques for Lemmings | Articles
                            The fox knows many things, but the hedgehog knows one big thing.

                            D Offline
                            D Offline
                            dandy72
                            wrote on last edited by
                            #15

                            Sometimes I'm just being a little bit too literal. Daniel's answer above suggests we're both on the same page on this one. :-)

                            Greg UtasG 1 Reply Last reply
                            0
                            • D dbrenth

                              My teacher asked me to write a program on the board and solve it. I wrote:

                              230 - 220 x 0.5

                              and announced that the answer was 5! My teacher claimed I was incorrect, but I was not. Can you please explain it to him? Thanks Hint: My teacher was quite embarrassed when I actually said the answer out loud.

                              Brent

                              O Offline
                              O Offline
                              obermd
                              wrote on last edited by
                              #16

                              The answer is 120. The way you get "5" is via a flaw in all four function calculators that don't follow basic math order of operations. By the way, the Windows calculator in Standard mode has this same flaw but it works properly in scientific mode.

                              1 Reply Last reply
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                              • L Lost User

                                dbrenth wrote:

                                Can you please explain it to him?

                                Dear Teacher, dbrenth is a cocky little so and so, who needs to be taken down a peg or two. ;P

                                O Offline
                                O Offline
                                obermd
                                wrote on last edited by
                                #17

                                And marked down for not completing the solution.

                                1 Reply Last reply
                                0
                                • C CPallini

                                  You teacher was right, and told you the correct result was actually 76. Could you please tell us why?

                                  "In testa che avete, Signor di Ceprano?" -- Rigoletto

                                  F Offline
                                  F Offline
                                  Fueled By Decaff
                                  wrote on last edited by
                                  #18

                                  I thought the answer was 78.

                                  C 1 Reply Last reply
                                  0
                                  • F Fueled By Decaff

                                    I thought the answer was 78.

                                    C Offline
                                    C Offline
                                    CPallini
                                    wrote on last edited by
                                    #19

                                    42. :-D

                                    "In testa che avete, Signor di Ceprano?" -- Rigoletto

                                    L 1 Reply Last reply
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                                    • D dandy72

                                      Sometimes I'm just being a little bit too literal. Daniel's answer above suggests we're both on the same page on this one. :-)

                                      Greg UtasG Offline
                                      Greg UtasG Offline
                                      Greg Utas
                                      wrote on last edited by
                                      #20

                                      Yeah, you're both on the AR page. :-D

                                      Robust Services Core | Software Techniques for Lemmings | Articles
                                      The fox knows many things, but the hedgehog knows one big thing.

                                      <p><a href="https://github.com/GregUtas/robust-services-core/blob/master/README.md">Robust Services Core</a>
                                      <em>The fox knows many things, but the hedgehog knows one big thing.</em></p>

                                      D D 2 Replies Last reply
                                      0
                                      • C CPallini

                                        You teacher was right, and told you the correct result was actually 76. Could you please tell us why?

                                        "In testa che avete, Signor di Ceprano?" -- Rigoletto

                                        D Offline
                                        D Offline
                                        Daniel Pfeffer
                                        wrote on last edited by
                                        #21

                                        Octal

                                        Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.

                                        C 1 Reply Last reply
                                        0
                                        • D Daniel Pfeffer

                                          Octal

                                          Freedom is the freedom to say that two plus two make four. If that is granted, all else follows. -- 6079 Smith W.

                                          C Offline
                                          C Offline
                                          CPallini
                                          wrote on last edited by
                                          #22

                                          Bravo!

                                          "In testa che avete, Signor di Ceprano?" -- Rigoletto

                                          1 Reply Last reply
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