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anonymous

  • one year ago

Annabelle and Navene are multiplying (4275)(4372). Annabelle's Work Navene's Work (4275)(4372) = 42 + 375 + 2 = 4577 (4275)(4372) = 42⋅375⋅2 = 46710 Is either of them correct? Explain your reasoning.

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  1. jtvatsim
    • one year ago
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    Well, let's start with Annabelle, do you think she is correct?

  2. anonymous
    • one year ago
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    gut feeling, yes

  3. jtvatsim
    • one year ago
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    OK, let's check that gut feeling now. So, multiplication is repeated addition, right? That's why 3*70 is 70 + 70 + 70. So, do you think it makes sense that 4275*4372 = 4577 if you think about it this way?

  4. jtvatsim
    • one year ago
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    Basically, you are adding 4372 a bunch of times 4372 + 4372 + 4372 + 4372 + 4372 + 4372 + 4372 + 4372 + 4372 + 4372 + ... Seems like chances are slim that this will add up to only 4577... :)

  5. jtvatsim
    • one year ago
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    Does that make sense? Do you still think Annabelle is correct?

  6. anonymous
    • one year ago
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    no

  7. jtvatsim
    • one year ago
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    Maybe I should have spread out my questions. :) No, it doesn't make sense. Or no Annabelle is wrong?

  8. anonymous
    • one year ago
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    no annabelle is wrong

  9. jtvatsim
    • one year ago
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    OK, great. I agree with that. :)

  10. jtvatsim
    • one year ago
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    Now Navene is doing something a little different... but let's see what we think...

  11. jtvatsim
    • one year ago
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    Before I go on, do you know the trick that if you multiply something by 10 you just add a 0 to the end? So, like 10*543 = 5430.

  12. anonymous
    • one year ago
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    yes

  13. jtvatsim
    • one year ago
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    OK, cool. To bust Navene's answer, I'm going to use a similar idea. I'll multiply by 100, which just adds two 0s instead of one. Look and see that (100)(4372) = 437200 this is already WAY bigger than Navene's answer of 46710. So (4275)(4372) has to be even bigger than (100)(4372). No way Navene, that's not right. Does that make sense to you?

  14. anonymous
    • one year ago
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    so there both wrong , can you do me a favor and sum that up into a paragraph

  15. imqwerty
    • one year ago
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    If there is something lime (a)(b) then it means a x b i.e, it means multiplication. So if we compare we can see that navene has expanded the problem properly but he has done some calxulation mistake due to which he gets the wrong answer

  16. jtvatsim
    • one year ago
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    Yes, they are both wrong. I'll let someone else take a shot at writing it up, but I think you can do it. Here are the main points: 1) Annabelle is wrong since multiplication is just repeated addition. 2) Navene is wrong since we know that multiplying by 100 adds two 0s. You can probably cut and paste from my previous explanations to make your own paragraph that makes sense to you. Show some calculations like I did to prove your point. Good luck!

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