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http://www.webmath.com/cgi-bin/k8ipcalc.cgi?op=mult&n1=808&n2=745&back=k8ipmult.html

Thank you.

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http://www.webmath.com/cgi-bin/k8ipcalc.cgi?op=mult&n1=808&n2=745&back=k8ipmult.html

Thank you.

- #2

Doc Al

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Because 5 x 8 gives 40, a two-digit answer.How come on step 3 it says to carry a 2nd 4?

You only need to carry if you end up with a two-digit number. Any number greater than 9 is two-digit.and What does it mean when it says that 40 is greater than 9? Where did the number 9 come from? What is it referring to?

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Thank you.

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Doc Al

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Doc Al

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And if you did add it, what would you get? I don't see a problem.

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44 instead of 40

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Doc Al

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How did you get that? You multiply 5 X 8 and get 40. It's two digits, so you don't think, you always carry. You write down the44 instead of 40

Of course, after some experience you will learn to peek ahead. If you are at the end of the line of digits, no point in carrying! But if you did--no problem, you still get the right answer.

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symbolipoint

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I didn't. I know how to do long handed multiplication. Who doesn't. And the answers are there anyways so obviously it's 40. I was saying...Don't you think it's a bad habit to carry the last 4 and put it beside the 8 because when you carry a number you're supposed to add it after multiplying the two numbers together...Which would be 5 X 8 + 4 = 44. I've never heard of carrying any numbers when you're done multiplying like it shows in this example. And it's completely pointless and would probably be confusing for a kid who's just learning. There is the potential for adding the last carried number to the last two numbers multipled. And you would come up with the wrong answer. I wasn't ever taught once to carry the last remainder so when I saw it in this example it looks like a mistake more than anything. Why would you carry the 4 when you just write 40 at the bottom anyways? It doesn't makse sense to go and add a 4 up there at all. How does that help?How did you get that?

- #11

Doc Al

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You are doing the carry operation incorrectly. When you multiply a digit you add whatever you carried from theDon't you think it's a bad habit to carry the last 4 and put it beside the 8 because when you carry a number you're supposed to add it after multiplying the two numbers together...Which would be 5 X 8 + 4 = 44.

There's nothing wrong with automatically writing down the 0 and carrying the 4. Of course, since there are no more digits to multiply*, you just get 5 X 0 = 0. Now add the 4 that you are carrying and you get 5 X 0 + 4 = 4. And you're done, with the correct answer.

*(Note that 808 can be written as 0808.)

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does anyone know a better algorithm?

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