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okay let's do a pounds formula lesson um
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I'm going to argue that this is the most
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important math problem you should know
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for your um wastewater operator career I
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mean there's a lot of important math
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problems absolutely I'm not saying the
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others don't matter but what I'm saying
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is a lot of what we do comes back to the
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pounds formula and uh when God I took my
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grade three and four I think definitely
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the grade the grade three math stood out
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a lot more to me than the grade four uh
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math did uh I had 15 math questions on
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the three and over half of them came
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back to this if I knew the pounds
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formula like the back of my hand I was
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in a good spot um and you can manipulate
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this to do a ton of different stuff it's
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not just you know what we're going to do
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here is pretty much grade one level
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stuff or Class C like really entry level
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stuff but when you get into more
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advanced uh things like a wasting rate
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if you know how to get back to a pound
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formula using percentages and um you
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know converting a percentage to a part
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per million uh you can figure out a
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wasting rate using a pound reverse
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pounds formula so just kind of a preview
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of what the capability of this formula
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is so you need a few things to
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get um the pie to work for you you need
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volume or flow in million gallons or
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million gallons per day so the if you're
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doing a volume it would just be million
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gallons if you need flow it's million
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or mg a concentration in parts per
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million or milligrams per liter I've
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never been tossed to parts per million
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or microgram per liter question but um
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just you know they're always change in
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the tests you never know so if that
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happens you need to get it to parts per
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million or milligrams per liter if
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you're going to use the Davidson Pi um
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and by the way these are synonymous for
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the sake of our math as you get through
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my videos you'll notice I have a
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preference for milligrams per liter just
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what how I like to express my
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concentration weight of one gallon of
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water is 8.34 pounds per gallon that is
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a constant that you need to know for the
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pounds formula it's a yeah so the the
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variables are going to be your volume or
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flow and concentration but your constant
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is the weight of a gallon of water
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because we're dealing with liquid uh
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pounds for the most part and so um yeah
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that's that's really why we use that so
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the Davidson Pi Works a certain way and
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I'll say this um this is the first and
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last time you seen me use a Davidson pie
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I I I think it takes up a ton of room
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but it's a wonderful uh tool to teach
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people how to do the pounds formula uh
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and what you do is you just multiply
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across the bottom and it spits the
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number out for you on the top it's
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pretty you'll see how it works it's very
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very simple um so let's do our first one
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this is going to be a standard pie where
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we're looking for the pounds we're given
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a volume of 500,000 gallons um and a
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concentration of 2 milligrams per liter
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dose it looks like of chlorine how many
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pounds of chlorine do we need in this
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Basin um it's not flow it's not gallons
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per day it's gallons well I need million
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gallons I need mg I I can't do this with
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gallons so I need to divide 500,000
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gallons by 1 million gallons per 1 mg
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you can see I've written it out in the
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latter method right here and the gallons
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cancel out and I'm given 0.5 mg if you
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have any confusion about this please ask
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in the comments uh the real the short
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answer is uh to to this issue is
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whenever you've got u a volume that is
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in gallons and you need it to get to mg
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or million gallons you just divide by a
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million and you're there um and some
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other math in the higher level test you
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might get be bumping into liters and
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stuff and if you can just get back to
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gallons and then divide by a million bam
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you're there you're ready to do a pounds
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formula okay we already have our
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concentration of 2 milligrams per liter
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8.34 * 2 Mig per liter or parts per
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million gives us put that in your put
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that in your calculator see if you can
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work it out .5 * 8.34 * 2 gives
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wow8 I don't know what's going on with
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my marker there 8.34 let's see if I got
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a little it might be getting a little
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dry 8.34 if you can't see that really
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8.34 uh pounds needed of
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Basin um so you might say well wait 8.34
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that's how much weight of one gallon of
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water is why is it the same well it's
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just kind of how my math shook out uh 2
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* 0.5 is 1 time 8.34 is 8.34 it's kind
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of a coincidence and actually I'm
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looking at this as I record this and I
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see I did the same thing with bigger
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numbers down here that's funny H I must
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just have a thing for fives and twos
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um okay so let's do our if you have any
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questions about this please ask in the
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comments below I'd be happy to answer
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any questions here about
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that okay our next math problem they're
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going to do this to you they're going to
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give you the pounds per day and you're
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going to either need to find the
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concentration or the flow and all you do
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is instead of multiply across the bottom
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you divide from the top down across the
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bottom okay so this is going to be uh
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we'll go over the numbers in a second
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but it would be this number divided by
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that divided by that gives me that or
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the other way around if they wanted to
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flow so we're going to work it out real
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8,340 pounds per day bod in a plant
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that's got a flow of 5 million gallons
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concentration uh of bod so all you do is
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take 8,340 pounds per day divided by 5
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million gallons per day divided by 8.34
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pounds per gallon work that out in your
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calculator and that is hopefully my
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up 200 milligrams per liter or parts per
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million you know pick your flavor um and
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as you can see uh like yeah I just kind
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of did this this was totally
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coincidental um I didn't I didn't mean
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for that to shake out like that but it
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did um 8340 lbs per day divided 5
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divided 8.34 gives us 200 migrs per
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liter that's our concentration and if
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they had asked for flow but given us the
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concentration you just go the other way
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okay and that's a great way to check
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your work when you're doing these during
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a test is uh do the math multiple ways
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and make sure you're getting the same
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numbers so if you get a pounds per day
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up here of 8.34 take that number and
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divide it back and see if the other
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numbers match up and if they don't check
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your work you might have you know fat
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fingered a calculator button or
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something I do that all the time um
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where I start getting into a Groove and
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I move too fast and then I you know
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check my work and go oh you know I do a
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lot of stuff fast I talk fast I work
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fast I I do my math fast so this is math
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is something that I have to rein myself
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in on anyway this is the one of the most
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important building blocks of the entire
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uh wastewater operator arsenal of
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knowledge is the pounds formula I can't
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emphasize that enough and this this
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launches into so many other math
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problems I I think I've already
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age chemical dosing just all sorts of
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stuff so um uh anyway with that please
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ask questions uh if you have any
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questions about how this works and if
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you want to uh discuss why it's the most
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important formula why I keep saying that
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I'd love to hear about your thoughts in
7:52
the comments below um also just a quick
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uh commercial for the Channel please
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people who need it share it with any of
8:01
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8:02
studying to take an exam please look me
8:05
up on LinkedIn it's in my profile links
8:08
below um and I'm you know lots of people
8:10
have actually found me there and and
8:12
asked me questions I try to get them as
8:14
fast as I can but this is kind of taken
8:16
off faster than i' expected so I'm
8:17
getting a lot of a lot of requests and
8:19
I'm just trying to keep up with it and
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uh you know keep up with life and day my
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day job and all that stuff as well so
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anyway I'm done rambling I hope this
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helps please ask any questions and we
8:30
will see you in the next one
