Subcategories

• Module 4 Day 2 Challenge Part 1

  Switching Digits of a Number

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• Module 4 Day 2 Challenge Part 2

  Variable Expressions, Factoring

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• Module 4 Day 2 Challenge Part 3

  Patterns, Factors, Simple Equations

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  Observations halfway through the video:

  I got 5, but from the fact that 50 reversed is 5, 50 - 5 = 45

  But anyways 5 was just like what Prof. Loh got

  Coincidence? I THINK NOT

  Also

  Prof. Loh's guess and check numbers

  74 - 47 = 27
  84 - 48 = 36
  92 - 29 = 63
  83 - 38 = 45

  All multiples of 9, and it seems that the higher number you start with, the higher your sum. It is just a general trend, of course, as you can see 84 - 48 was a lot lower than 83 - 38.

  But...

  Coincidence? I THINK NOT

  And as it turns out... I thought right

  Coincidence?

• Module 4 Day 2 Your Turn Part 1

  Trick for Multiplying 117 × 113, Mental Math

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  For this problem a solution that could possibly be used is using divisibility rules. Note how 117 is a multiple of 9 which automatically means that and number that 117 multiplies (in this case 113) Has to be a multiple of 9 as well. Note then how only i.) is a multiple of 9 out of all three solutions, therefore the only possible solution.

• Module 4 Day 2 Your Turn Part 2

  Using Variables to Express the Pattern

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• Module 4 Day 2 Your Turn Part 3

  Why the Trick Works

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  Great question! The trick really only works as long as

  The units digits of the two numbers sum to 10, and The rest of the numbers, apart from their units digits, are the same.

  ... like you could try writing 62 and 64 as 60+2 and 60+4, but when you multiply them the terms won't add and cancel nicely like they did in Prof. Loh's explanation.

  I hope that made sense to you; if it didn't I'd be happy to clarify. 😀

  This trick is slightly related to Difference of Squares, but also very different. It does not actually currently have a name... so I guess you could call it Prof. Loh's Trick. 😂

• Module 4 Day 2 Your Turn Part 4

  Why the Trick Works

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