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  • #31
    Re: Could you please check my math?

    The most accurate answer is with staying with the fractions:

    3 1/5 X 1 1/4 x 1 1/3~~ 16/5X5/4X4/3 = 320/60 = exactly 5 1/3


    When you convert 1/3 to decimal, then you have to decide how many places to carry, and it never comes out exact. It is, however, close enough for government work!

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    • #32
      Re: Could you please check my math?

      Originally posted by Aaron91 View Post
      Alright, so my 5 years of union apprenticeship school has started and I'm excited for it. I'm taking math now and wanted to make sure I had these right.

      1. 3 1/5 x 1 1/4 x 1 1/3 = ? I got 5 1/3.

      2. 11 1/4 divided by 2 1/2 = ? I got 4 1/2.
      I was at the Sox game last night, missed the party.

      There are two ways to do it, all mentioned above.
      I personally take a problem like this and convert to decimals, which makes it easier to do on the fly in my head.

      "1. 3 1/5 x 1 1/4 x 1 1/3 = I got 5 1/3."

      3.2 X 1.25 X 1.333 = 5.332 (5-1/3)

      Years ago I was a machinist, it was common to have to convert decimals to fractions in your head when sizing inserts & bits for a job...it's second nature for me to convert fractions to decimals when I do any problem like this.

      This may NOT necessarily be the way they want you to learn it though.

      In plumbing school, an example was on circular and radial volume or surface area.

      I grew up using PI (3.1415) as the formula to figure out volume, perimeters and surface area.

      In school they taught us to use .7854 rather than PI.

      You'll want to stick to the "book" on how they teach you to problem solve, in the future the way you resolve formulae will interact with other, more advanced things they teach you.

      Later, as you get into blueprints, learn offsets and sizing, you'll need to be on the same page as everyone else....especially where it's union.
      Last edited by DuckButter; 09-14-2008, 02:31 PM.

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      • #33
        Re: Could you please check my math?

        Originally posted by Aaron91 View Post
        Ben, to me that's dumbing down the trade to the hack level.

        Plumbing has alot of math in it, and I would like to use my head not my cell phone.

        Sorry for applying myself at work.
        I gotta say, I'm ecstatic to see you learning all this, however, Ben has a point.

        In the field, you'll be using a calculator...your boss isn't gonna wait while you write out long division or attempt square roots on the job.

        In school, a different story...we had to do square roots on paper as well as everything else.

        Again, do EXACTLY what they teach you, you'll be fine.

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        • #34
          Re: Could you please check my math?

          I was just helping a friend's son do college algebra over the phone the other night. It is amazing that once you learn how to do it, it just seems to come back to you.

          It is always good to know math. I needed to know how much my shoes were going to be when I applied the discount when shoes are on sale
          I love my plumber

          "My Hero"

          Welcome, Phoebe Jacqueline!

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          • #35
            Re: Could you please check my math?

            www.math.com
            sigpic

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            • #36
              Re: Could you please check my math?

              Originally posted by DuckButter;175126
              [B
              In school, a different story...we had to do square roots on paper as well as everything else.[/B]
              I never learned how to do that, but don't feel too bad about that.

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              • #37
                Re: Could you please check my math?

                Originally posted by cpw View Post
                I never learned how to do that, but don't feel too bad about that.
                Even the instructor told us the only reason we were learning it was so it would be on the notes we turned in after the test.

                They have since allowed calculators into the test...

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                • #38
                  Re: Could you please check my math?

                  Originally posted by Aaron91 View Post
                  Alright, so my 5 years of union apprenticeship school has started and I'm excited for it. I'm taking math now and wanted to make sure I had these right.

                  1. 3 1/5 x 1 1/4 x 1 1/3 = ? I got 5 1/3.

                  2. 11 1/4 divided by 2 1/2 = ? I got 4 1/2.
                  Calculators are great but you will miss the point of the lesson

                  Check this out

                  Attached Files

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                  • #39
                    Re: Could you please check my math?

                    Originally posted by Aaron91 View Post
                    Alright, thanks again guys.

                    82. It says...

                    Divide 13/16 by 5 1/5 and multiply the quotient by 6 2/3.

                    I understand that as...

                    13/16 divided by 5 1/5 x 6 2/3 = ?

                    First off, did I understand the problem right?

                    Second, can you please break this down because I'm lost on this one.

                    Thanks.
                    Is this making sense?

                    Basically any numerator (top of fraction) can be divided into or by any denominator (bottom of fraction) anywhere in the multiplication chain, this is why you can divide out the 16 and 20 by 4 to get 4 and 5 (see example) likewise 13 and 26 are divided by 13 to get 1 and 2.
                    Basic rule what ever you do to the top you do to the bottom and the result must stay the same.

                    Check your results with a calculator, i even messed thois one up on the first try. You will have loads of extra time if you learn this method, I bet it took you a while to figure out that 1.04166666 was 1 1/24

                    Attached Files

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                    • #40
                      Re: Could you please check my math?

                      Originally posted by Aaron91 View Post
                      Have fun with your 1/2" copper and 4" pvc cause that's all your gonna work with, with an attitude like that Dunbar.
                      Kind of a hard tack Aaron
                      Dunbar was only kidding.Nothing angled at your yute.

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                      • #41
                        Re: Could you please check my math?

                        Math like this is pointless and is only for mental exercise. What the heck is 1/5 of an inch? Why is it important in the construction trade to be able figure out a fraction that isn't able to be divided by a 16th. These numbers are useful for cooking but in 12 years of construction have never needed to do these equations.

                        1/2" copper and 4" pvc for me!!!
                        Buy cheap, buy twice.

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                        • #42
                          Re: Could you please check my math?

                          Just forgot that surveyers divide number by 10 for their dumpy level and philly rod but I've never met a plumber that needs that kinda math.
                          Buy cheap, buy twice.

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                          • #43
                            Re: Could you please check my math?

                            i need help too

                            but i'll phrase it in real plumbing terms.

                            if i can hand cut, ream, thread and screw a 1'' black steel pipe in 66 seconds

                            and aaron can do it in 1 minute 45 seconds.

                            who is faster and by how much time

                            p.s. aaron,
                            i did watch the video and eating your words are pretty tasty

                            keep up the excitement level with school and you'll be done faster than you know. i enjoyed all 4 years when i went.

                            i'll help you with your soldering homework

                            rick.
                            phoebe it is

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                            • #44
                              Re: Could you please check my math?

                              Rick by 39 seconds
                              Buy cheap, buy twice.

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                              • #45
                                Re: Could you please check my math?

                                I nominated this because this is one of the best math threads I've ever seen! In woodworking, these problems come up ALL the time. I'm sure these kinds of problems are frequent in plumbing as well. Rule of thumb for vent stack is all well and good, but how do you KNOW it's going to work in that 5-story apartment building? Even when following code, I'm sure you can end up with some serious problems in plumbing.

                                Thanks to everyone that's posted hints and tips on fractional mathematics. I've always had problems with that subject.
                                I put it all back together better than before. There\'s lots of leftover parts.

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