Dividing Two-Digit NumbersDate: 03/01/2002 at 17:32:40 From: Callie Subject: Math How do you divide 2-digit numbers? Date: 03/01/2002 at 18:46:01 From: Doctor Ian Subject: Re: Math Hi Callie, You know how multiplication is just repeated addition? 12*11 = 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11 + 11 11*12 = 12 + 12 + 12 + 12 + 12 + 12 + 12 + 12 + 12 + 12 + 12 Well, division is kind of like repeated subtraction. For example, if I want to divide 121 by 11, I can do this: 121 - 11 Subtract 1st time --- 110 - 11 2nd --- 99 - 11 3rd --- 88 - 11 4th --- 77 . . --- 22 11th - 11 --- 11 - 11 12th --- 0 That is, the following are just two ways of saying the same thing: _____ 1) 11 ) 121 = 12 2) 11 subtracted 12 times from 121 is zero So when you don't know what else to do, you can use this definition. For example, 1 1 1 ____ 24 ) 79 24 That's 1 -- 55 24 That's 2 -- 31 24 That's 3 -- 7 Remainder Answer = 3 remainder 7 Now, note that you don't _have_ to do the subtractions 1 at a time. In this example, you might see right away that 2 * 24 must be less than 79: 1 2 ____ 24 ) 79 48 That's 2 -- 31 24 That's 3 -- 7 Remainder Answer = 3 remainder 7 Or - and this is what your teacher _wants_ you to do - you might do enough math in your head to figure out that 3 is the LARGEST value it could possibly be: 3 ____ 24 ) 79 72 That's 3 -- 7 Remainder Answer = 3 remainder 7 But that _is_ kind of a pain, and the more digits that are involved, the bigger pain it is. In the end, you get the same answer no matter how many subtractions you have to do. As you get more practice, you'll get better at guessing things like how many times 24 will go into 79; but I would say, at first, don't sweat it. It's more important to understand what's actually going on, even if it means you do a few more steps, than to memorize 'how to do division' without understanding it. Does this make sense? Write back if any of this isn't clear, or if you'd like to talk about it some more. - Doctor Ian, The Math Forum http://mathforum.org/dr.math/ |
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