Mathlopnik [Edit]

"ttyymmnn" (ttyymmnn) 09/15/2020 at 23:01 • Filed to: None

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Trying to help my son with his math. I get the idea here, but I can’t make it to the finish.

Trying to figure out what CE is.

It looks to me like CE = (BD + DE) - BC

But that’s where my math skills fail me.

Update: I was right all along, I just screwed up on my algebra. Thanks to all who chimed in.

Highlander-Datsuns are Forever > ttyymmnn 09/15/2020 at 22:40

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The graphics for this problem are terrible. They should be ashamed. 

Phyrxes once again has a wagon! > ttyymmnn 09/15/2020 at 22:41

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I’m not a math teacher but I’m known to pretend to be one (Physics Teacher).

BC = 3x+47

BD = 27+x

CE = x+26

DE = 10

BD+10=BC+CE

27+x+10 = 3x+47+x+26

Solve for x?
The equation solver from G oogle said x was -12 so going with that

Plug in to find CE?
I get 14, which seems reasonable if DE is 10.

Who is the Leader - 404 / Blog No Longer Available > ttyymmnn 09/15/2020 at 22:41

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I don’t quite get that. It seems as though BD is less than BC when you would obviously want to find the difference between BD and BC so you can set the sides with concrete numbers equal to each other.

WilliamsSW > ttyymmnn 09/15/2020 at 22:41

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X is -12

fintail > ttyymmnn 09/15/2020 at 22:42

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Poor_Sh > ttyymmnn 09/15/2020 at 22:42

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Done in my head but is x=-9?

Slant6 > ttyymmnn 09/15/2020 at 22:43

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I keep telling myself I’ll teach myself some math, take some prerequisite courses, and go back to school for something engineering related.

Saw this post and gave up on my dreams. Not your fault, it was inevitable, but I have no desire to put myself through this again. 

ItalianJobR53 - now with added 'MERICA and unreliability > ttyymmnn 09/15/2020 at 22:43

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CD = CE - DE = BD - BC

CE - DE = (x + 26) - 10 and BD - BC = (3x +47) - (27 + x) and both of these are equal to each other

Solve this equation to get x and then find CD and then CE

Roadkilled > ttyymmnn 09/15/2020 at 22:44

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BC is 3x+47

CE is x+26

BD is 27+x

DE is 10

The whole length is BC+CE and it is also BD+DE.

Therefore, 3x+47 + x+26 = 27+x + 10.

Simplifying, 4x+73 = x + 37.

Subtract x from both sides to get 3x+73 = 37.

Subtract 73 from both sides to get 3x = -36.

Divide by 3 to get x = negative 12.

So CE is x+26 which is 14.

Earlier tonight, my son asked for help with his pre-calculus homework, so this doesn’t seem so bad.

shop-teacher > ttyymmnn 09/15/2020 at 22:45

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I don't have any paper handy to try and solve this, but I think the equation to find x would be: (3x+47)+(x+26)=(27+x)+10

pip bip - choose Corrour > ttyymmnn 09/15/2020 at 22:48

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“ Think of a number

Add that number again

Multiply by 3

Divide by 2

Subtract the number you first thought of

And the answer is 3, the inflation rate is 3 percent mr treasurer”

‘That’s not right’

“No, but it’s clever”

ttyymmnn > Phyrxes once again has a wagon! 09/15/2020 at 22:48

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My wife got -12. She’s much smarter than I am. 

ttyymmnn > WilliamsSW 09/15/2020 at 22:48

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No credit unless you show your work. 

ttyymmnn > fintail 09/15/2020 at 22:49

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Been there. 

Poor_Sh > Poor_Sh 09/15/2020 at 22:49

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Lol shit I got to 3x = -36 and thought -36/3 = - 9 not - 12. Dammit, not bad for head math at 11pm though

ttyymmnn > Slant6 09/15/2020 at 22:50

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As a musician, all I have to do is count to three.

ttyymmnn > Roadkilled 09/15/2020 at 22:50

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My wife got -12 too. She’s a lot smarter than me. 

OPPOsaurus WRX > ttyymmnn 09/15/2020 at 22:51

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CE=x+26

CE=CD+DE

CD=CE-DE, CD=26+X, DE=10

26+X =CE-10

CE=X+36

I dunno where I’m going.  

ttyymmnn > pip bip - choose Corrour 09/15/2020 at 22:52

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Slant6 > ttyymmnn 09/15/2020 at 22:53

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As an industrial designer I get to keep a calculator at my desk, and my work rarely requires any more from me than basic arithmetic .

Denver Is Stuck In The 90s > ttyymmnn 09/15/2020 at 22:56

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is this the new math they keep talking about?

ttyymmnn > Denver Is Stuck In The 90s 09/15/2020 at 23:03

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No, it’s old math because I was actually able to figure it out. I just made a basic algebra mistake. It’s been 35 years since I did this sort of thing, and I failed one semester of it. 

barnie > Slant6 09/15/2020 at 23:12

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My Dad (RIP) told me as a youngster; “Math is a language used to discuss relationships.”. No idea if it’s original with him but it shaped me. I never learne d more than trig but I’m not afraid to apply math the anything. And I can see the world as planes, angle, axis, etc. Always have though little beats a good sunset . Or pretty girls - o h yea, tri angles and stuff...

For Sweden > ttyymmnn 09/15/2020 at 23:14

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Math is for nerds who can't carry a tune tbh

gmporschenut also a fan of hondas > ttyymmnn 09/15/2020 at 23:16

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I get 14

BC is “A”

CD is “F”

DE is “g”

F+ G=x+26 move G over, F=-10 +( x+26)

f=x+16

A+F=27+x, substitute in “ f=x+16" and “ A=3x+47" and solve X = -12

take that F+G=x+26, F=4. So add to 10 and I get 14 for F+ G or CE

ttyymmnn > gmporschenut also a fan of hondas 09/15/2020 at 23:19

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-12. I made my critical error in step two when I forgot to distribute the negative to both the 3x and 47. 

WilliamsSW > ttyymmnn 09/15/2020 at 23:35

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I absolutely hated that rule in school, because I could do most of it in my head and I hated writing.  

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > ttyymmnn 09/15/2020 at 23:44

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I did ok in math up to algebra, I think I got a B. After that I was like, the fuck am I looking at here?? I’m a more artistic person, I did my best. For rigging or graphics I sometimes have to do some math and I check it a few times to make sure.

gmporschenut also a fan of hondas > ttyymmnn 09/15/2020 at 23:44

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Systems of equations give me mild PTSD from finite element analysis (fea) each point of data or node woud be a variable. Thus every variable would need another equation to solve for. Each problem would be 10+ variables to solve for and would be pages long. I killed so many trees that semester. Now i use a computer in minutes have 10k points and a fancy 3d image

ttyymmnn > WilliamsSW 09/15/2020 at 23:46

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Here’s my work. I screwed up initially when I forgot to make the 47 negative. Distributive property FTW. 

ttyymmnn > 415s30 W123TSXWaggoIIIIIIo ( •_•))°) 09/15/2020 at 23:48

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I failed a semester of algebra in high school, probably because I was smoking too much dope. I took one algebra class in my first year of college, got a C, and never took another class. 

Chariotoflove > ttyymmnn 09/15/2020 at 23:49

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I like this as a decently designed and no terribly difficult problem to teach algebra.

ttyymmnn > Chariotoflove 09/15/2020 at 23:52

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Decently designed because even I could do it. Well, I could figure out the concept, but failed in my basic “solve for x” skills.

415s30 W123TSXWaggoIIIIIIo ( •_•))°) > ttyymmnn 09/15/2020 at 23:56

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They made me take quantitative reasoning in college, it was like statistics. I don’t think I did very well but I must have passed. I wish I was better at math, there are a lot of tests to do things, even though you don’t really use it when you do that actual job.

Chariotoflove > ttyymmnn 09/15/2020 at 23:59

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Eh, that happens. I like the problem because it sets out principles without all the distracting frippery that often accompanies story problems and scares students. This is kind of an in between problem that you could easily imagine being a story problem. Good training wheels for real life application of algebra.

ttyymmnn > Chariotoflove 09/16/2020 at 00:15

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My son can manipulate the variables, but where he struggles is conceptualizing the problem. There were other ones where I told him to draw out the lines based on the verbal description. Once you do that, it’s a lot easier. 

Chariotoflove > ttyymmnn 09/16/2020 at 00:20

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Yes, some people are visual learners and that helps a lot.

Shoop > ttyymmnn 09/16/2020 at 01:00

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(27+x)+10=(3x+47)+(x+26) and solve for x

Plug into x+26

Shoop > Shoop 09/16/2020 at 01:04

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Basically there's 2 ways to get the full length, so you set them equal. 

Wolfram says x=-12

CE=14

Shoop > ttyymmnn 09/16/2020 at 01:05

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Definitely not. 

ttyymmnn > Shoop 09/16/2020 at 01:08

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My thinking was right, my algebra was flawed. I did manage to get it right, with some help from my smarter half. 

TheRealBicycleBuck > ttyymmnn 09/16/2020 at 07:43

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It’s easier if you take smaller bites and always write out the line segments first. CE = CD + DE. Then fill in what you know. (x+26) = CD + 10. Solve for CD. After that, do it again on the left side. BD = BC +CD. (27+x) = (3x+47) + CD. Solve for CD. Then set the two CD equations equal to each other and solve for x.

It’s much easier to learn if you walk through all of the steps. That’s the only way we could get our son through algebra. Getting him to write it out was difficult since he could do a lot of the math in his head. The problem was locating the errors when it wasn’t written down.

gmporschenut also a fan of hondas > TheRealBicycleBuck 09/16/2020 at 09:13

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My HS physics teacher used to rock point if you didn’t list out all your known variables and units  at the beginning of a problem

And that was a tough habit to break if not writing down.

Shoop > Slant6 09/16/2020 at 09:22

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Yeah man, if you want to do something engineering related, and this stuff scares you, it's probably not the right choice. 

ttyymmnn > TheRealBicycleBuck 09/16/2020 at 10:15

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It works both ways. My wife used your method. Mine worked just fine, except that I forgot to distribute the negative. Simple algebra mistake. I actually enjoy doing problems like this because it’s a bit like a puzzle. I might have done fewer steps in my solution by combining steps, but I like to do one thing at a time and write it out. 

TheRealBicycleBuck > ttyymmnn 09/16/2020 at 10:44

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The difference is in the level of thinking required. What we’ve seen in our kids’ homework is that they (both the people putting together the lessons and our kids) often forget a step, miss a step, overlook a step, or do it in their head, making it difficult or impossible to identify the error. It’s really annoying when the examples in the homework do this. My son has said to me, “ They went from THIS, to THIS, but I don’t understand WHY!”

My perspective is heavily influenced by my experience with programming. Everything has to be explicitly stated. If it isn’t, then the program either doesn’t work or spits out bogus information. Granted, there are plenty of black boxes where you feed the software information and it spits out a result, but you can usually find out what’s happening in that box and double-check the results by another means.

Slant6 > Shoop 09/16/2020 at 11:16

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Its not so much that I’m scared, more that I don’t like dealing with it if I don’t have to. Right now I’m and Industrial Designer, so an engineer with lower stakes/ someone else checks my work.

Been thinking of going back to  school for an Masters in Architecture and a lot of the schools have a Pre Calc and Physics course requirement that I don’t have. I can do them, I just don't want to use my free time for them. 

ttyymmnn > TheRealBicycleBuck 09/16/2020 at 11:29

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My boys hate showing their work. One of the twins in particular works too fast and makes mistakes. We’re working on him. His brother tends to be more methodical and less hyper-brained. It’s actually fascinating how two allegedly identical children can be so different in temperament. 

Slant6 > Shoop 09/16/2020 at 11:33

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Upon actually looking at the posted problem I was able to solve it on my own. I just saw math and didn't want to do it. I can do it, I just had a bad experience with math growing up and learned to avoid it whenever possible. I've also adapted pretty well to CAD doing all my practical math for me. 

Shoop > Highlander-Datsuns are Forever 09/16/2020 at 11:46

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I disagree. It's well laid out, and it takes a second to pull the relevant info out. There's even multiple approaches to solving for x

ttyymmnn > TheRealBicycleBuck 09/16/2020 at 14:34

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It was way simpler than either of us made it. Definitely one of those “once you see it” things. In class today, the teacher said:

CD + DE = BC + CE

Plug and chug, solve for x.

Four lines of math instead of the seven I used in my original solution.

TheRealBicycleBuck > ttyymmnn 09/16/2020 at 15:18

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Hah!

Well, we just proved there’s more than one way to skin a cat!

ttyymmnn > TheRealBicycleBuck 09/16/2020 at 15:21

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There are at least three. But I think the biggest lesson we came away with was that we were fixated on finding out what CE is ( x + 26) when we should have been concentrating on what x is. Definitely a major change in the frame of reference for that problem, and perhaps math in general.