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Grading Proofs in Geometry


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Am I the only one who finds this really difficult? It seems like there's always either a slight difference in wording, or two steps done in different order, etc. that make it really hard to tell if it's correct.

 

It seems like my only choices are to work through the problem myself to follow what he's done (not gonna happen -- I'm too dumb and slow at anything math-like and don't have that many hours!) or just figure that if it looks close enough, it's probably okay 'cause he's a pretty smart kid.

 

Any thoughts, suggestions, or just commiseration?

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I've subscribed to this to see what others have to say. I missed Geometry in high school (well, got half a year's worth and then moved from a nonsemester school to a semester one, so I count it as not at all) and will be doing this next year. I don't know if I'll have time to learn it with her, but have a solution manual.

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There is never only one way to prove anything in mathematics. This is one of the irritating aspects of those two column proofs that students see in a basic geometry class. Students often convinced themselves that there is but a single method of proof.

 

Sorry, but a teacher has no choice but to read through the proofs and follow the logic, in my opinion. If you don't have the time to do this, have your student explain some proofs to you. Obvious flaws should be apparent. Ask for justifications of statements beyond "because of that theorem on page 189". Even good students will take the easy way out sometimes, so I would scan work regularly. Perhaps not every bit of it, but look at some weekly and have him explain some of the proofs; you'll have a good idea of where he stands.

 

What you won't have with this method is a numeric grade on homework. Is that important to you?

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There is never only one way to prove anything in mathematics. What you won't have with this method is a numeric grade on homework. Is that important to you?

 

Thanks for all of your answer. Not that I'm happy to hear it, but of course it makes sense. Perhaps I'll have to give up the forum or something in orde to tackle geometry. Or I'll give up reading and study it at the poolside. Fun...actually, I may end up liking it. Or maybe not.

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Parents have a tough time grading the homework, especially the proofs and the constructions. It takes me LOTS of time to get thru grading homework -- I have 15 students in my class this year!!

 

Our text makes use of partially done, you fill in some blanks, flow-chart style proofs at times, which tend to be easier to correct. The ones that are do-it-yourself are tougher on me.

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There is never only one way to prove anything in mathematics. This is one of the irritating aspects of those two column proofs that students see in a basic geometry class. Students often convinced themselves that there is but a single method of proof.

...

What you won't have with this method is a numeric grade on homework. Is that important to you?

 

Having only ever had a basic geometry class, I didn't know there was anything but two column proofs! Thanks for the suggestions on grading. I will make use of them. I do need numeric grades... if not on homework, at least on quizzes and tests, but what I'll do is grade on carefulness and 'does it make sense?'-ness, instead of whether it's exactly the same as the solution manual.

 

Thanks.

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Am I the only one who finds this really difficult? It seems like there's always either a slight difference in wording, or two steps done in different order, etc. that make it really hard to tell if it's correct.

 

It seems like my only choices are to work through the problem myself to follow what he's done (not gonna happen -- I'm too dumb and slow at anything math-like and don't have that many hours!) or just figure that if it looks close enough, it's probably okay 'cause he's a pretty smart kid.

 

Any thoughts, suggestions, or just commiseration?

 

Just commiseration here! It stinks! And we're only on chapter 1............:001_huh:

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I found myself in a similar circumstance and I just wanted to encourage you to take the time to figure out the proofs. If I remember correctly, you do have others coming after this one (actually I think I'm thinking of Karin after reviewing this thread - but maybe you do as well), so your time invested will pay off.

 

My son is fairly gifted but occasionally has logic lapses and I think it would be a disservice of being at home to let him continue in "faulty" thinking. As Jane says, there are various ways of solving the proofs, but it is impossible for the book to put them all and you want your "child" to have that creative way of thinking out of the book to be able to offer other possibilities but not all answers that our children can dream up are actually correct. So they do need to be checked and you don't want him to end up taking a test to find out that he has been doing it wrong all the time....

 

It has been work for me as well, but possible. When I took geometry in high school, it was the last class before sports. I would be sitting there with butterflies in my stomach the whole class time, especially before a race, and did extremely poorly. But now these proofs are starting to look easy!

 

Best,

Joan

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I do have another child coming, although I'm strongly leaning toward outsourcing her geometry, as (imagine a loving but realistic tone here) she is one of the most stubborn and difficult kids to teach I've ever encountered/heard of/imagined... you get the picture!

 

I have been trying to follow the logic of (as Jean suggested) some of the proofs. I've also taken to handing him the solutions manual, and having him read through their proofs, so he can see another way to do it. I've tried to communicate that this isn't because his are wrong, but because I want him to see that there is more than way way to approach a problem, and the solution manual may have a more efficient method than his.

 

Thanks so much for the encouragement.

 

Blessings.

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Same here, only with algebra. I'm going through it with dc and I'm constantly amazed that I can actually do these blasted problems - now that I'm 52 years old!!! Why couldn't I do this back in 8th grade when my brain was young and new?!?!!, I'm thinking as I get one right answer after another!

 

Anyway, just wanted to let you know that it's worth the effort.

 

HTH.

 

My concern is that my brain could easily do them when my brain was young and new, but will it be able to handle it now that I'm in my late 40s????? Philosophy has become very easy, but it's not particularly logical, IMO. Well, not consistently logical. Geometry. Hmm, I'd rather learn Calculus, but I'm sure I need to redo other math to get there as I'm rusty, rusty, rusty.

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unless lets say statement 3 is another given. I always helps my son that his next statement needs to be based upon his previous (or several previous) statements or reasons. If often helps to put which previous statement or reasons you are citing in ( ) with your statement. If you make a statement with no backup then you have holes and your proof doesn't work. For example my ds has problems with this concept of right angles

Lets say angle A and Angle B are right angles so he will then say that Angle A is equal to angle B , but he has a hole. He has not said all right angles are equal. This seem obvious but it must be stated. Hence the joy of proofs. Early on in proofs we spent a lot of time talking them out, cutting them, coloring them etc. If seems this is paying off as we get to more difficult one as he is doing very well with Jacobs.

Karen

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