TXMary2 Posted August 31, 2010 Share Posted August 31, 2010 (edited) So, the answer key for Key to Algebra is annoying me. Has anyone else used this and found errors? I am not great at Algebra to begin with and I need the key to be right!! When multiplying integers - the rule is postive x negative = negative right? Also, negative x negative = positive right? So the key says (-3)(-3)(-3) = -27 but it shoud be +27 right? Am I right or am I missing something? Another one says 6 x -5 x -3 = 90 but shouldn't it be -90 ??? My son doesn't need this confusion!:banghead: Edited to add: OK- nevermind. I have had my coffee and I see clearly now. It's just another moron morning over here!! Edited August 31, 2010 by TXMary2 Quote Link to comment Share on other sites More sharing options...
Danestress Posted August 31, 2010 Share Posted August 31, 2010 So, the answer key for Key to Algebra is annoying me. Has anyone else used this and found errors? I am not great at Algebra to begin with and I need the key to be right!! When multiplying integers - the rule is postive x negative = negative right? Also, negative x negative = positive right? So the key says (-3)(-3)(-3) = -27 but it shoud be +27 right? Am I right or am I missing something? Another one says 6 x -5 x -3 = 90 but shouldn't it be -90 ??? My son doesn't need this confusion!:banghead: (-3)(-3) is positive. 3. Then that(3)(-3) is negative. So the answer is -27. (6)(-5) is (-11). That (-30)(-3) will result in a positive. 90. Quote Link to comment Share on other sites More sharing options...
Jann in TX Posted August 31, 2010 Share Posted August 31, 2010 (-3)(-3)(-3) the first 2 are multiplied to get a positive 9-- now you have (+9)(-3) and positive times a negative is a negative so result is -27 For the second one :6 x -5 x -3 6 x (-5) = -30 (-30) x (-3) = + 90 negative times a negative is a positive. You can only multiply 2 numbers together at one time when you have 'strings' of multiplication. Both of your problems require 2 steps. Quote Link to comment Share on other sites More sharing options...
Chris in VA Posted August 31, 2010 Share Posted August 31, 2010 the rule is postive x negative = negative right? Also, negative x negative = positive right If that is so, then -3times-3 would equal +9. +9times-3 would equal -27. Quote Link to comment Share on other sites More sharing options...
abbeyej Posted August 31, 2010 Share Posted August 31, 2010 No, the answers in the book are correct. Your statement above is correct too. A negative times a negative is a positive. And a negative times a positive is a negative. But a negative times a negative times a negative is a negative... ;) An odd number of negative multipliers will give you a negative number. And even number of negative multipliers will give you a positive number. Think about it in words, if that helps. I like Sarah Lee is positive. I don't like Sarah Lee is negative. "Nobody doesn't like Sarah Lee" (the old ad campaign) is positive -- it means that *everybody* likes Sarah Lee. But if "It's not true that nobody doesn't like Sarah Lee," takes you back to a single negative: somebody doesn't like Sarah Lee. But if you said, "It's not untrue that nobody doesn't like Sarah Lee," then once again the ultimate *meaning* of your statement is positive: everybody likes Sarah Lee... It goes on and on forever. Two negatives cancel each other out. A third makes the whole negative again. Odd numbers of negatives = a negative. And a trick for this? Just imagine two subtraction symbols ganging up to make an addition symbol. :) So if you have: (-5)(-3)(-2)(-7)(-2)= (+5)(3)(+2)(7)(-2)= (5)(3)(2)(7)(-2)= -420... But if you have:(-5)(-3)(-2)(-7)(-2)(-1)= (+5)(3)(+2)(7)(+2)(1)= (5)(3)(2)(7)(2)(1)= 420... Quote Link to comment Share on other sites More sharing options...
TXMary2 Posted August 31, 2010 Author Share Posted August 31, 2010 (edited) :banghead::banghead: UGH! OK- I see that now. Thank you. I think I will go have my coffee now. Edited August 31, 2010 by TXMary2 Quote Link to comment Share on other sites More sharing options...
Chris in VA Posted August 31, 2010 Share Posted August 31, 2010 Just wanted to say that you made my day by asking an algebra question I can actually answer! LOL Quote Link to comment Share on other sites More sharing options...
TXMary2 Posted August 31, 2010 Author Share Posted August 31, 2010 Just wanted to say that you made my day by asking an algebra question I can actually answer! LOL Gee, glad I could help. :tongue_smilie: LOL Quote Link to comment Share on other sites More sharing options...
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