View Full Version : Geometry help

hockeymom

02-28-2014, 11:30 AM

When measuring angles, how much leeway do you give? I usually say as long as he gets it within a couple of degrees it's close enough, but I'm not sure it's the right approach. Sometimes what we get is quite different than what the answer guide (MM 6) gives us, though.

I feel like accuracy should be really important, but what's realistic?

Thanks!

MrsLOLcat

02-28-2014, 11:50 AM

It's a workbook. I remember getting different answers than the teacher when I took geometry. She gave us leeway if it was within 5 degrees. She said if we were in the 'real world,' we'd have bigger scales to work with and more accurate tools. It was the only thing she did that I liked, but I remember the relief I felt when she said that rule...

dbmamaz

02-28-2014, 11:50 AM

idk, i always double-check, but there was one Raven did which just seemed totally wrong. I honestly dont trust geometry texts as far as measuring angles - i feel like its just too easy for the books to print the wrong angle and it not get caught. we just do our best and get the concept. Realistically, when is that skill used?

inmom

02-28-2014, 11:52 AM

I think your approach is just fine. measuring with protractors isn't an accurate proposition anyway. If it is really off, though, check to make sure he's reading the correct scale (upper vs. lower).

Norm Deplume

02-28-2014, 12:18 PM

I can't imagine plastic school protractors are really all that accurate. If it's pretty close, I'd let them slide.

Just for reference's sake: Khan Academy has angle-measuring exercises that need to be at the correct measurement, but they're always on the "5s". They have angle-estimating exercises that ask the student to be accurate within 15º.

hockeymom

02-28-2014, 12:43 PM

Thank you! That approach has always seemed okay to me in earlier grades, but there's this small part of me that worries about how his papers would be graded at a b and m school, or what if he grows up to be an engineer and can't accurately measure angles? But yeah, I guess he wouldn't be using a 99 cent protractor from Target!

Thanks for the reassurance. It helped take a lot of stress off of him this morning. :)

fastweedpuller

02-28-2014, 01:19 PM

Hockeymom, your post reminded me that I was looking into getting something to supplement my kid's apparent love of geometry and I ran across this when looking for a quickie cheapo workbook from Key Curriculum:

The Geometer's Sketchpad (http://www.keycurriculum.com/)

Watch that splashpage for a while. The graphics are so cool, boy could I have used it in my geometry class in high school (even though I got all As); it helps actually seeing it, you know? But yeah it is more expensive than your 99c protractor :)

dbmamaz

02-28-2014, 02:03 PM

but also, on a test, if the answer key was wrong, the teacher would notice that most of the kids had the same wrong answer and check it, or be able to explain why it was wrong. i'm not even sure we did measuring of angles in high school? maybe?

murphs_mom

02-28-2014, 02:26 PM

Thank you! That approach has always seemed okay to me in earlier grades, but there's this small part of me that worries about how his papers would be graded at a b and m school, or what if he grows up to be an engineer and can't accurately measure angles?

I think that as long as Common Core is around, he'd be fine in B&M school. According to that approach, all he really needs is a firm understanding of the process. The answer is secondary.

IMO, for the youngers set, I agree that it's a correct answer as long as it's within 3 (or even 5) degrees. As they get older, though, the accuracy will hopefully improve.

As to 'when' someone would need to be able to measure accurate angles, I wished I was MUCH better at calculating accurate angles when we were renovating the house. I did the crown moulding, chair rail, baseboards, window trim, and tile floor (created a pattern w/cut tile), and it would have saved me $$ if I'd been better at the angle thing. I've also needed to calculate angles when doing stained glass/mosaic work. It is a good skill to have.

Avalon

02-28-2014, 06:37 PM

I'm so sorry, this is wildly off-topic, but I can't help laughing out loud whenever I see "b & m" school. Unfortunately, "BM" is my mother-in-law's term for "bowel movement," so whenever I see "b&m schools" I automatically think it must be a really shitty school :D!

crunchynerd

03-09-2014, 10:25 AM

I'm so sorry, this is wildly off-topic, but I can't help laughing out loud whenever I see "b & m" school. Unfortunately, "BM" is my mother-in-law's term for "bowel movement," so whenever I see "b&m schools" I automatically think it must be a really shitty school :D!

And in Maine, it's the name of an old, old baked beans factory and brand: B&M Baked Beans. HAHA!

crunchynerd

03-09-2014, 10:29 AM

I can't imagine plastic school protractors are really all that accurate. If it's pretty close, I'd let them slide.

Just for reference's sake: Khan Academy has angle-measuring exercises that need to be at the correct measurement, but they're always on the "5s". They have angle-estimating exercises that ask the student to be accurate within 15º.

Was also going to mention Khan Academy, because I'm going through it alongside my daughter (and as her coach) and their methods practically by definition, have to reflect what your kid would encounter in school or on standardized tests, so would be a good way to ensure your kid is familiar with, and can meet, those expectations. They are also adding free SAT, GMAT, etc test prep now, for all comers.

aspiecat

03-24-2014, 11:10 AM

If you're measuring, leeway is fine, usually within a few degrees. As another poster said, IRL one has far more sophisticated tools with which to work, so accuracy is possible (and necessary). In the classroom, simply proving you know what you're doing is all teachers require.

If you're working angles out with rules of Geometry, accuracy is important. Eg, rules of vertically opposite, complementary, or supplementary angles mean you have no excuse for inaccuracy.

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