Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
Skins
  • Light
  • Cerulean
  • Cosmo
  • Flatly
  • Journal
  • Litera
  • Lumen
  • Lux
  • Materia
  • Minty
  • Morph
  • Pulse
  • Sandstone
  • Simplex
  • Sketchy
  • Spacelab
  • United
  • Yeti
  • Zephyr
  • Dark
  • Cyborg
  • Darkly
  • Quartz
  • Slate
  • Solar
  • Superhero
  • Vapor

  • Default (No Skin)
  • No Skin
Collapse

The New Coffee Room

  1. TNCR
  2. General Discussion
  3. Puzzle time - the Triangle

Puzzle time - the Triangle

Scheduled Pinned Locked Moved General Discussion
13 Posts 7 Posters 125 Views
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • jon-nycJ Online
    jon-nycJ Online
    jon-nyc
    wrote on last edited by jon-nyc
    #1

    A teacher (lets call him Klaus) used to give this problem as part of his elementary geometry class:

    A right triangle has hypotenuse (BC) of length 10, and a height (AP) of length 6. What is the area?

    5C5B3817-9600-458A-8DCB-B097BB0A4362.jpeg

    His average students (lets call them Horace and Ax) got full credit for the answer 1/2 * 10 * 6 = 30.

    But a really smart kid (lets call her Taiwan girl) couldn’t solve the problem.

    Why not?

    Thank you for your attention to this matter.

    1 Reply Last reply
    • AxtremusA Offline
      AxtremusA Offline
      Axtremus
      wrote on last edited by Klaus
      #2

      :::

      There are three hypothenuses. Which one has the length 10?

      :::

      1 Reply Last reply
      • KlausK Offline
        KlausK Offline
        Klaus
        wrote on last edited by
        #3

        :::

        Is it something as boring as "it isn't specified that AP is the height, so it could be something slightly different"?

        :::

        1 Reply Last reply
        • jon-nycJ Online
          jon-nycJ Online
          jon-nyc
          wrote on last edited by
          #4

          @Axtremus BC has length 10

          @Klaus AP is the height.

          Thank you for your attention to this matter.

          1 Reply Last reply
          • KlausK Offline
            KlausK Offline
            Klaus
            wrote on last edited by Klaus
            #5

            Oh, now I see.

            :::

            AB isn't the hypotenuse.

            :::

            1 Reply Last reply
            • jon-nycJ Online
              jon-nycJ Online
              jon-nyc
              wrote on last edited by
              #6

              Nope that was just a typo on my part when I went back to clarify!

              Thank you for your attention to this matter.

              1 Reply Last reply
              • kluursK Offline
                kluursK Offline
                kluurs
                wrote on last edited by kluurs
                #7

                ||AC represents the height - as the triangle is inverted for triangle CAB. 6 is the height of triangle PAB. ||

                1 Reply Last reply
                • AxtremusA Offline
                  AxtremusA Offline
                  Axtremus
                  wrote on last edited by
                  #8

                  :::

                  I was trying to say that the “really smart” kid cannot solve the problem because of the ambiguity stemming from there having three possible right triangles in the diagram: ABC, ACP, ABP. So when you say something like the hypothenuse has length 10, it’s ambiguous whether you’re referring to which hypothenuse, AB, AC, or BC.

                  :::

                  1 Reply Last reply
                  • NunataxN Offline
                    NunataxN Offline
                    Nunatax
                    wrote on last edited by
                    #9

                    :::

                    Too lazy to look up the required formulas right now, but with A fixed as a right angle and CB equal to 10, height AP will be confined to a certain range. I guess it's at its maximum when angles C and B are both 45 degrees and even then AP will likely be less than 6? If that's the case, the scenario is simply impossible.

                    :::

                    1 Reply Last reply
                    • jon-nycJ Online
                      jon-nycJ Online
                      jon-nyc
                      wrote on last edited by jon-nyc
                      #10

                      I should have named the smart kid Nunatax.

                      The triangle is impossible as this simple diagram shows us:

                      ED5C7B88-5A4F-4177-B4A3-861F6FEDAA50.jpeg

                      (Recall that, if the angle CAB is a right angle, it must lie on the perimeter of the circle, per Euclid

                      The maximum height of AP is 5.

                      Thank you for your attention to this matter.

                      taiwan_girlT 1 Reply Last reply
                      • KlausK Offline
                        KlausK Offline
                        Klaus
                        wrote on last edited by Klaus
                        #11

                        Nice!

                        I wonder what that restriction (of the maximal height) looks like in non-Euclidean geometries.

                        1 Reply Last reply
                        • MikM Away
                          MikM Away
                          Mik
                          wrote on last edited by
                          #12

                          The original formula would only work if CAB was a right triangle anyway, or 1/2 a rectangle.

                          "The intelligent man who is proud of his intelligence is like the condemned man who is proud of his large cell." Simone Weil

                          1 Reply Last reply
                          • jon-nycJ jon-nyc

                            I should have named the smart kid Nunatax.

                            The triangle is impossible as this simple diagram shows us:

                            ED5C7B88-5A4F-4177-B4A3-861F6FEDAA50.jpeg

                            (Recall that, if the angle CAB is a right angle, it must lie on the perimeter of the circle, per Euclid

                            The maximum height of AP is 5.

                            taiwan_girlT Offline
                            taiwan_girlT Offline
                            taiwan_girl
                            wrote on last edited by
                            #13

                            @jon-nyc said in Puzzle time - the Triangle:

                            I should have named the smart kid Nunatax.

                            Correct, you should not have picked me! 555

                            1 Reply Last reply
                            Reply
                            • Reply as topic
                            Log in to reply
                            • Oldest to Newest
                            • Newest to Oldest
                            • Most Votes


                            • Login

                            • Don't have an account? Register

                            • Login or register to search.
                            • First post
                              Last post
                            0
                            • Categories
                            • Recent
                            • Tags
                            • Popular
                            • Users
                            • Groups