Adding ShortcutDate: 05/05/2003 at 22:29:25 From: Jessica Subject: Finding a sum Explain how 10 helps you find the sum of 9 and 8. Date: 05/06/2003 at 17:06:22 From: Doctor Peterson Subject: Re: Finding a sum Hi, Jessica. One way to add a pair of numbers like this is to go to ten and then see how much more is left to add. I'll demonstrate by adding 8 + 5: We start with 8. That is 2 less than 10, so if we add 2 to the 8, we get to 10. But we want to add 5; that is 3 more than 2. So after we add 2, we have 3 more to add to the 10; and the answer is 13. Here is a picture: ________5________ / \ 8 2 3 +-------------------------------+------>|---------->| +---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 It's a lot easier to think about than to write! If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/ |
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