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We now have the general tools to really tackle any

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multiplication problems.

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So in this video I'm just going to do a ton of examples.

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So let's start off with-- and I'll start in yellow.

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Let's start off with 32 times 18.

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Say 8 times 2 is 16.

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Well, I'll do it in our head this time because you always

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don't have all this space to work with.

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So 8 times 2 is 16.

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Put the 1 up there.

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8 times 3 is 24.

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24 plus 1 is 25.

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So 8 times 32 was 256.

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Now we're going to have to multiply this 1, which is

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really a 10, times 32.

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I'll underline it with the orange.

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1 times 2-- oh, we have to be very careful here.

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1 times 2 is 2.

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So you might say hey, let me stick a 2 down there.

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Remember, this isn't a 1.

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This is a 10, so we have to stick a 0 there

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to remember that.

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So 10 times 2 is 20.

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Or you say 1 times 2 is 2, but you're putting it in the 2's

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place, so you still get 20.

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So 10 times 2 is 20.

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It works out.

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Then 1 times 3.

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And we have to be very careful.

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Let's get rid of what we had from before.

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1 times 3 is 3.

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There's nothing to add here, so you just get a 3.

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And so you get 10 times 32 is 320.

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This 1 right here, that's a 10.

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10 plus 8 is 18.

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So now we just add up the two numbers.

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You add them up.

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6 plus 0 is 6.

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5 plus 2 is 7.

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2 plus 3 is 5.

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Let's keep going.

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Let's do 99 times 88.

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So a big number.

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8 times 9 is 72.

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Stick the 7 up there.

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And then you have 8 times 9 again.

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8 times 9 is 72, but now you have the 7 up here.

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So 72 plus 7 is 79.

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Fair enough.

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Now we're done with this.

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Let's just delete it just so that we don't get confused

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in our next step.

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In our next we're going to multiply this 8 now times 99.

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But this 8 is an 80.

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So let's stick a 0 down there.

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8 times 9 is 72.

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Stick a 7 up there.

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Then 8 times 9 is 72.

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Plus 7 is 79.

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2 plus 0 is 2.

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Let me switch colors.

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9 plus 2 is 11.

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Carry the 1.

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1 plus 7 is 8.

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8 plus 9 is 17.

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Carry the 1.

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1 plus 7 is 8.

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8,712.

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Let's keep going.

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Can't do enough of these.

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All right, 53 times 78.

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I think you're getting the hang of it now.

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Let's multiply 8 times 53 first.

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So 8 times 3 is 24.

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Stick the 2 up there.

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8 times 5 is 40.

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40 plus 2 is 42.

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Now we're going to have to deal with that 7 right

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there, which is really a 70.

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So we got to remember to put the 0 there.

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7 times 3, and let's get rid of this.

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Don't want to get confused.

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7 times 3 is 21.

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Put the 1 there and put the 2 up here.

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7 times 5 is 35.

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Plus 2 is 37.

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Now we're ready to add.

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4 plus 0 is 4.

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2 plus 1 is 3.

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4 plus 7 is 11.

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Carry the 1.

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1 plus 3 is 4.

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4,134.

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Let's up the stakes a little bit.

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So let's say I had 796 times 58.

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Let's mix it up well.

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All right, so first we're just going to multiply 8 times 796.

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And notice, I've thrown in an extra digit up here.

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So 8 times 6 is 48.

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Put the 4 up there.

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8 times 9 is 72.

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Plus 4 is 76.

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And then 8 times 7 is 56.

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56 plus 7 is 63.

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I'm sure I'll make a careless mistake at some

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point in this video.

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And the goal for you is to identify if and when I do.

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All right, now we're ready, so we can get rid of

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these guys up here.

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Now we can multiply this 5, which is in the 10's place.

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It's really a 50.

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Times this up here.

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Because it's a 50 we stick a 0 down there.

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5 times 6 is 30.

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Put the 0 there, put the 3 up there.

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5 times 9 is 45.

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Plus the 3 is 48.

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5 times 7 is 35.

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Plus 4 is 39.

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Now we're ready to add.

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8 plus 0 is 8.

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6 plus 0 is 6.

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3 plus 8 is 11.

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1 plus 6 is 7.

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7 plus 9 is 16.

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And then 1 plus 3 is 4.

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So 796 times 58 is 46,168.

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And that sounds about right because 796-- it's almost 800.

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You know, which is almost 1,000.

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So if we multiplied 1,000 times 58 we'd get 58,000.

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But we're multiplying something a little bit smaller than 1,000

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times 58, so we're getting something a little bit

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smaller than 58,000.

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So the number is in the correct ballpark.

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Now let's do one more here where I'm really going

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to step up the stakes.

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Let's do 523 times-- I'm going to do a three-digit number now.

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Times 798.

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That's a big three-digit number.

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But it's the same exact process.

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And once you kind of see the pattern you say, hey, this'll

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apply to any number of digits times any number of digits.

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It'll just start taking you a long time and your chances of

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making a careless mistake are going to go up, but

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it's the same idea.

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So we start with 8 times 523.

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8 times 3 is 24.

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Stick the 2 up there.

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Now 8 times 2 is 16.

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16 plus 2 is 18.

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Put the 1 up there.

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8 times 5 is 40.

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Plus 1 is 41.

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So 8 times 523 is 4,184.

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We're not done.

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We have to multiply times the 90 and by the 700.

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So let's do the 90 right there.

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So it's a 90, so we'll stick a 0 there.

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It's not a 9.

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And let's get rid of these guys right there.

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9 times 3 is 27.

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9 times 2 is 18.

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18 plus 2 is 20.

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And then we have 9 times 5 is 45.

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45 plus 2 is 47.

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I don't want to write that thick.

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47.

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Let me make sure I did that one right, and let's just

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review it a little bit.

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9 times 3 was 27.

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We wrote the 7 down here and put the 2 up there.

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9 times 2 is 18.

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We added 2 to that, so we wrote 20.

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Wrote the 0 down there and the 2 up there.

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The 9 times 5 was 45.

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Plus 2 is 47.

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You really have to make sure you don't make careless

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mistakes with these.

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Then finally, we have to multiply the 7, which is

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really a 700 times 523.

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When it was just an 8 we just started multiplying here.

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When it was a 90, when we were dealing with the 10's

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place, we put a 0 there.

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Now that we're dealing with something that's in the

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100's, we're going to put two 0's there.

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200
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And so you have 7-- and let's get rid of this stuff.

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That'll just mess us up.

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7 times 3 is 21.

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Put the 1 there.

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Stick the 2 up there.

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7 times 2 is 14.

206
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14 plus our 2 is 16.

207
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Put the 1 up there.

208
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7 times 5 is 35.

209
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Plus 1 is 36.

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211
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And now we're ready to add.

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And hopefully we didn't make any careless mistakes.

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So 4 plus 0 plus 0.

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That's easy.

215
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That's 4.

216
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8 plus 7 plus 0.

217
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That's 15.

218
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Carry the 1.

219
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1 plus 1 plus 1 is 3.

220
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4 plus 7 plus 6.

221
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That's what's?

222
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4 plus 6 is 10.

223
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It's 17.

224
00:09:43,950 --> 00:09:46,580


225
00:09:46,580 --> 00:09:48,920
And then we have 1 plus 4 is 5.

226
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5 plus 6 is 11.

227
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Carry the 1.

228
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1 plus 3 is 4.

229
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So 523 times 798 is 417,354.

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Now we can even check to make sure.

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And so this is the moment of truth.

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Let's see if we have-- let's see.

233
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523 times 798.

234
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There you go.

235
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Moment of truth.

236
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I don't have to re-record this video.

237
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It's 417,354.

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But we did it without the calculator, which is

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the important point.