Esse Quam Videri Posted February 17, 2014 Share Posted February 17, 2014 We figured it out by reasoning and trial/error. Is there a better way (there usually is)? What are two numbers if the sum of the two numbers is 6.5 and their product is 0.64? Quote Link to comment Share on other sites More sharing options...
kbutton Posted February 17, 2014 Share Posted February 17, 2014 Do you have a specific problem number for this? Sometimes I can figure out what they want me to do by what section it's in. I have this book and would try to look it up. We're not there yet. These are the only types of problems in the IP that bug me to death. Quote Link to comment Share on other sites More sharing options...
RebeccaMary Posted February 18, 2014 Share Posted February 18, 2014 I think that, for this level, trial-and-error is best. Otherwise, you'd probably have to use the quadratic equation. So, if: a + b = 6.5 a x b = 0.64 then: a = 6.5 – b and: (6.5 – b) x b = 0.64 so: 6.5b – b^2 = 0.64 and b^2 - 6.5b + 0.64 = 0 Using the quadratic equation, you get: a = 6.4 and b = 0.1 As far as I know, the quadratic is not yet part of the SM 4B scope & sequence, so I'd agree with sticking with the intuitive approach! Quote Link to comment Share on other sites More sharing options...
Posted February 18, 2014 Share Posted February 18, 2014 We figured it out by reasoning and trial/error. Is there a better way (there usually is)? What are two numbers if the sum of the two numbers is 6.5 and their product is 0.64? The IP and especially CWP books can be tough. I think the text it trying to teach some abstract thinking about numbers here. Bar diagrams aren't going to help. So, you know the product is < 1. What kind of multiplicands yield a result < 1? At least one of them has to be < 1. But they both can't be, because their sum is 6.5. So, the larger number has to be within 1 of 6.5. But if the smaller one is closer to 1 (but still < 1), the multiplication doesn't work out. etc. etc. etc. So, I think you did the right thing with reasoning + trial/error. Sometimes when we're doing Singapore Math, we get the right answer, but follow the "wrong" way. As long as the thinking is mathematically sound, and we're not missing anything, I think that's OK. Quote Link to comment Share on other sites More sharing options...
daybreaking Posted February 18, 2014 Share Posted February 18, 2014 We figured it out by reasoning and trial/error. Is there a better way (there usually is)? What are two numbers if the sum of the two numbers is 6.5 and their product is 0.64? I'm wondering if the reasoning in this problem is supposed to reinforce an understanding of decimal place value. When I looked at the problem, I immediately noticed (ignoring the decimal points) that 64 is one away from 65. Then I thought that 64 + 1 = 65 and 64 x 1 = 64. From there, I added back in the decimal points to get 6.4 + .1 = 6.5 and 6.4 x .1 = .64 Quote Link to comment Share on other sites More sharing options...
kbutton Posted February 18, 2014 Share Posted February 18, 2014 I'm wondering if the reasoning in this problem is supposed to reinforce an understanding of decimal place value. When I looked at the problem, I immediately noticed (ignoring the decimal points) that 64 is one away from 65. Then I thought that 64 + 1 = 65 and 64 x 1 = 64. From there, I added back in the decimal points to get 6.4 + .1 = 6.5 and 6.4 x .1 = .64 This would be my guess. I am going to have to remember this when I get to this point in the book. I wish they gave more hints or example problems of this. I don't think trial and error is what they want usually. Quote Link to comment Share on other sites More sharing options...
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