![]() (20 x 40 = 800) is the same as saying 2x4 is 8 with two powers of ten or two place values or even two zeros but just don't say adding two zeros. *** Third we start to understand multiplying by powers of ten. Not to mention that adding a zero doesn't change the value of anything (additive property of zero) what you mean is that you are adding a place value. Imagine how that screws up kids who are working with decimal places - adding a zero doesn't change the values at all if it is behind the decimal. ![]() This means that we add a place value make it one place bigger. 2x2 is the same as 2x20 - just ten times bigger. Everything else is just a repeat by powers of 10. ** Third lets reinforce the idea that the only facts we need to know are the on the times table up to 9x9. * Second kids are reinforcing place value and the idea that multiplying big numbers is not a big deal. ![]() FIrst the weirdness of telling kids who just learned that the 4 (of 42) and the 2 (of 29) are in the tens place and called forty and twenty - of now telling them that they are a 4 and 2 and just multiply by four and multiply by two - that is absent from this method. 29 x 42 - 18 (2 x 9 = 18) 40 (2 x 20 = 40) * 360 (40 x 9 = 360) ** + 800 (40 x 20= 800)*** - 1218 With the partial products method the confusion of "carrying" a number to the tens place or hundreds place is eliminated. ![]() When I say partial products this is what I mean. ![]()
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