kalanamak Posted February 16, 2011 Share Posted February 16, 2011 Math was so little and so long ago. :tongue_smilie:I have no idea if my study guide is being idiotic or I'm missing something basic. The study guide is usually not idiotic. This is for a formula where you have to calculate something like: 0.48/ the square root of 0.8. I am used to doing this with a calculator. I won't have one during my test. Is there a pencil and paper way of figuring that the s.r. of .8 is .8944? I have looked online for this formula, but they all assume you have a calculator. Quote Link to comment Share on other sites More sharing options...
Liz CA Posted February 16, 2011 Share Posted February 16, 2011 Math was so little and so long ago. :tongue_smilie:I have no idea if my study guide is being idiotic or I'm missing something basic. The study guide is usually not idiotic. This is for a formula where you have to calculate something like: 0.48/ the square root of 0.8. I am used to doing this with a calculator. I won't have one during my test. Is there a pencil and paper way of figuring that the s.r. of .8 is .8944? I have looked online for this formula, but they all assume you have a calculator. Have you checked Lial's website? I am thinking of breaking it down to prime numbers but I can't remember what to do with decimals. Quote Link to comment Share on other sites More sharing options...
LidiyaDawn Posted February 16, 2011 Share Posted February 16, 2011 All I can think is "why?" ~ as in, why would a person ever have to figure something like that out? :p dd14 and I have that convo - "but mom, whyyyyy do i need to learn this?" and I give "well you might need it someday" .. "yeah, like for what?" me ---> :001_huh: "Aha! What if you decide to me an astronaut or something?" her ---> :thumbdown: "Cuz the book says so?" (not helpful, I realize that lol) Quote Link to comment Share on other sites More sharing options...
regentrude Posted February 16, 2011 Share Posted February 16, 2011 (edited) All I can think is "why?" ~ as in, why would a person ever have to figure something like that out? If you continue in higher math and science, you may have to simplify an expression like this that contains SYMBOLS, not numbers - so doing it with a calculator will be impossible. This is a problem about rationalizing the denominator and using properties of the square root to simplify. The numbers are just to practice the skills. What kind of a test is this? Usually, the intent of the problems is to simplify as far as possible - so in all situations I have encountered leaving it as 0.24 * sqrt(5) is fine. (I have not come across anything where they wanted me to actually calculate a numerical value for sqrt (5) without a calculator) Edited February 16, 2011 by regentrude Quote Link to comment Share on other sites More sharing options...
Perry Posted February 16, 2011 Share Posted February 16, 2011 (edited) What kind of a test is this? Usually, the intent of the problems is to simplify as far as possible - so in all situations I have encountered leaving it as 0.24 * sqrt(5) is fine. :iagree: Although I would have done it differently. I would multiply both numerator and denominator times sqrt .8 (.48) * sqrt .8/ (sqrt .8)^2 since (sqrt .8)^2= .8, you now have (.48)*sqrt .8/ .8 Since 8 is a common factor of .8 and .48, you can simplify the .48/.8 as 6/10, or .6 Now you have (sqrt .8)* .6 You can further simplify the sqrt .8 as sqrt (4*.2), and since the sqrt of 4 =2, you now have (.6*2) *sqrt .2 =1.2*sqrt .2 Although maybe it's not considered simplified if there is a decimal inside the radical. It looks confusing, but I think if you write it out with the radical sign it will make more sense. Edited February 16, 2011 by Perry Quote Link to comment Share on other sites More sharing options...
kalanamak Posted February 16, 2011 Author Share Posted February 16, 2011 I What kind of a test is this? Board re-cert. http://en.wikipedia.org/wiki/QT_interval It is correcting the QT interval for the heart rate. In the OLD days, I did it with a calculator. Now the EKG machine does it. Why my(expensive and carefully edited very dense) study guide spends *3 precious paragraphs* on how the RR interval HAS to be in seconds, not ms, and how, if QT is not right around 40% of the RR one should calculate it, I'm not sure, and it has me wondering. Looking at the explanations, I can't believe we would be required to calculate it. I certainly would have remembered if I had had to do it 10 years ago on the last test. Quote Link to comment Share on other sites More sharing options...
Perry Posted February 16, 2011 Share Posted February 16, 2011 If this pops up on the PSAT, the student won't have the time if the goal is finishing. Mental math should be used to do the ops in less steps: 0.48/sqrt0.8 is 0.48/(sqrt(4/5))=0.24*sqrt5 and done versus 0.48/sqrt0.8 is 0.06sqrt0.8= 1.2sqrt0.2 still needs simplified. Key is having sufficient experience w/ rationalizing and fractions.:) Your way is definitely more efficient! But I can do it my way in a few seconds because it's so familiar to me and I do most of those steps in my head, so I'm sticking with it. :D Quote Link to comment Share on other sites More sharing options...
LidiyaDawn Posted February 16, 2011 Share Posted February 16, 2011 All I can think is "why?" ~ as in, why would a person ever have to figure something like that out? If you continue in higher math and science, you may have to simplify an expression like this that contains SYMBOLS, not numbers - so doing it with a calculator will be impossible. This is a problem about rationalizing the denominator and using properties of the square root to simplify. The numbers are just to practice the skills. No, I meant it in the way of "where in real life would you ever find yourself needing to do that?" ;) ~ like what I said about the convos dd14 and I have sometimes. In this case, if "finding the square root of decimals less than one" comes up in her math at some point, I can say: "what if you want to be a doctor and need to find a QT heart rate thingamajig?" :p Quote Link to comment Share on other sites More sharing options...
Perry Posted February 16, 2011 Share Posted February 16, 2011 Your way is definitely more efficient! But I can do it my way in a few seconds because it's so familiar to me and I do most of those steps in my head, so I'm sticking with it. :D Also, it works with *any* number, not just an "easy" number like .8=4/5. You sort of have to do it the long way if it's .8/sqrt .68 Quote Link to comment Share on other sites More sharing options...
Perry Posted February 16, 2011 Share Posted February 16, 2011 (edited) I agree with you, and I am a big fan of shortcuts. But since the OP didn't know how to do these types of problems, taking a shortcut with this one won't help her generalize to other problems of this sort. Your way works in this case, because you can easily turn .8 into a fraction with the numerator being a perfect square. In the real world, that would be unusual. Maybe it isn't unusual on a test though. It's funny, I was thinking of EM too. And one of my big issues with EM is that they don't develop the general algorithm that is useful in *all* situations, but use "pretty" numbers that turn out not to be very useful in the real world. It reminds me of the article Where's the Beef in the Turkey Problem? Edited February 16, 2011 by Perry Quote Link to comment Share on other sites More sharing options...
regentrude Posted February 16, 2011 Share Posted February 16, 2011 No, I meant it in the way of "where in real life would you ever find yourself needing to do that?" ;) ~ like what I said about the convos dd14 and I have sometimes. In this case, if "finding the square root of decimals less than one" comes up in her math at some point, I can say: "what if you want to be a doctor and need to find a QT heart rate thingamajig?" :p Depends on what you call "real life". I am a physicist and my real life had plenty of complicated math I needed to do my research. And quite some math to do my teaching. "real life" is not just grocery shopping. For most people it includes a career, and in many STEM career fields, this kind of math is a standard everyday tool to their work. Quote Link to comment Share on other sites More sharing options...
Guest Dulcimeramy Posted February 16, 2011 Share Posted February 16, 2011 Depends on what you call "real life".I am a physicist and my real life had plenty of complicated math I needed to do my research. And quite some math to do my teaching. "Real life" is not just grocery shopping. For most people it includes a career, and in many STEM career fields, this kind of math is a standard everyday tool to their work. :iagree: and Amen. Did you know that in 2011 electricians are having a hard time with unemployment, but in just a few years the nation will be desperate for qualified electricians? Homeschoolers should keep this in mind. Your educated child might be interested in a well-paying job in 10 or 15 years, and there won't be much competition. My husband attended a symposium last year on the future of the trade and came home looking mighty grim. These facts were discussed: 1. The vast majority of today's electricians will be retiring within a decade. Who will replace them? 2. The vast majority of those who apply for apprenticeships can not pass the math portion of the exams. 3. The vast majority of those who do pass the tests find during their first year that they can not do the mental math required on the job. My husband knows that this is all true because he works with apprentices every day. Over the past 15 years he has watched the literacy and numeracy of incoming electricians drop to frighteningly low levels. Journeyman electricians use lots and lots of trigonometry. They think algebraically. They don't do math in groups, either, and there is no one to check their figures. They have to just know what they are doing mathematically and how to apply math skills to real life situations. Everyone wants to act like construction workers are the uneducated folk who couldn't go to college, but that is baloney. Some of these construction jobs require an awful lot of technology and math. The IBEW requires completion of a bachelors of science as part of the apprenticeship program. Quote Link to comment Share on other sites More sharing options...
LidiyaDawn Posted February 16, 2011 Share Posted February 16, 2011 No, I meant it in the way of "where in real life would you ever find yourself needing to do that?" ~ like what I said about the convos dd14 and I have sometimes. In this case, if "finding the square root of decimals less than one" comes up in her math at some point, I can say: "what if you want to be a doctor and need to find a QT heart rate thingamajig?" :p Depends on what you call "real life". I am a physicist and my real life had plenty of complicated math I needed to do my research. And quite some math to do my teaching. "real life" is not just grocery shopping. For most people it includes a career, and in many STEM career fields, this kind of math is a standard everyday tool to their work. Okay, this is kinda getting off track ~ but see, we're not a physicist sort of family. That's about the best way that I can put it :laugh: -- and hey, it's not meant negatively. I've never known a physicist before; it's actually pretty cool that you are. :D (what are "STEM career fields?") For our kids, "real life math" does indeed mean the day to day applications ~ balancing a household budget, banking, household maintenance, USING the budget, etc. It's all good though ~ and my initial post was really just meant as a light joke about the kind of math being presented. :) Quote Link to comment Share on other sites More sharing options...
kalanamak Posted February 16, 2011 Author Share Posted February 16, 2011 I wasn't trying to show the OP how to simplify the expression; I was merely trying to answer her question and show how to find the square root of a decimal less than one. Hopefully I answered that sufficiently; perhaps she'll leave feedback. . I decided it was a quirk of the study-guide writer (who is quirky). There is just no way that much math is going to be on a minute-a-problem test, and as I already have 150 flash cards each JAMMED with facts I have to memorize on just cardiology, I'm going to have to muster on. Thanks, and I hope you enjoyed yourself stretching the mind on "the rack of thought". :001_smile: Quote Link to comment Share on other sites More sharing options...
regentrude Posted February 16, 2011 Share Posted February 16, 2011 (edited) (what are "STEM career fields?") Science, Technology, Engineering, Math For the kids' "real life" picture: These are the people who invented and built computers, iPods, cell phones, Wiis, cars, power plants. The people who can program the 3-d special effects for the new movies ;-) I'm sure some of those must occur in their lives :001_smile: (And I am serious: particularly for families who don't have a lot of connection to science and engineering, I find it very important that the kids have an idea what these professions do. How else can they decide if they maybe want to be one when they grow up?) Edited February 16, 2011 by regentrude Quote Link to comment Share on other sites More sharing options...
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