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Welcome to Brainfuse!

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We can review multiplying integers by solving this problem on screen: A cafeteria

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added 4 tables to the dining area

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If each table can seat 5 people

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How many more people can sit in the cafeteria now?

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Draw the tables

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There's one, and we can just cut and paste

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to add the next four.

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There are our four tables

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And we know that each table

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Can seat 5 people.

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To find out how many more people can sit in the cafeteria at this point, we just need to add the number 5 four times.

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So 5 plus 5 is 10, plus 5 is 15, plus 5 equals 20

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That's actually what you do when you multiply 5 times 4

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To save time and your wrist, you can use multiplication to solve problems like this one

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In a multiplication problem, the numbers you are multiplying are each called factors

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And the answer is called the product.

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Let's look at a few other examples of multiplication problems

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We'll delete that problem, too.

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Let's practice by trying these examples. We have 38 times 5.

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I'm going to use place value, I'll write the tens

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digits in blue and the ones digits in red. So, 38

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times

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5

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is just another way to say that the number 38 needs to be added 5 times in a row.

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And 15 times 24. That gives you a simple way to add the number 15, 24 times in a row.

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But it would not be fun to write that out. So instead of doing these lengthy addition problems, make sure to

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Memorize your multiplication tables for the numbers 1 to 12

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Once you know the times tables well, you can take on any multiplication problem.

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So let's practice by trying these examples.

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To set up multiplication problems, make sure to line up the digits in the ones place, the digits in the tens place, and so on.

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So 38 times 5.

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We have the 8 and the 5 in the ones place and the 3 in the tens place.

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Ok, so 5 ones times 8 ones, or 8 times 5 is equal to 40

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Or 4 tens and 0 ones, so I can write that zero in the ones place,

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And the 4 in the tens place

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So I can write that zero in the ones column and the 4 in the tens column

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Next I have 5 ones x 3 tens

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Which is the same as saying

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5 times 30

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And that equals 150

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So I can write the zero in the ones column

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the 5 in the tens column

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And the 1

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In the hundreds column

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Okay, now we just find the sum of these 2 numbers

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0 plus 0 is 0, 4 plus 5 is 9 and

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1 plus 0 is 1

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So our product of 38 times 5 is 190

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So the next one is a little bit more challenging because it involves two double digit numbers, not

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just one. Again, we need to line up the digits in the ones place

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so that's

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5 and 4 and the digits in the tens place

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1 and 2.

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We start by multiplying the number on the bottom right that's 4 ones times 5 ones

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or 4 times 5, which is equal to 20

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or 2 tens, 0 ones

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So we write 0 ones and write a 2 in the tens column. Then we have 4 ones times 1 ten,

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Which is like saying 4 times 10, and that's equal to 40

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So we write the

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4 in the tens column

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And a zero in the ones column

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So next we move to the 2

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And you need to multiply 2 tens

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By 5 ones, so that's like saying 20 times 5

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So that would be

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100

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0 in the ones column

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0 in the tens column and

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move into the hundreds column

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Put the 1

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Next, we have 2 tens times 1 ten. And 10 is a user-friendly factor because you need to

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just add a 0

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To the other factor

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That's 2 tens, or 20,

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in order to find their product. So 20 times 10 equals 200

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2 in the hundreds column,

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0 in the tens column

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And a 0 in the ones column. Now again, we just find the sum of these numbers

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0 plus many 0s is 0

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2 plus 4 is 6, and 2 plus 1 is 3. So our product is 360

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As with addition, you don't need to worry about the order of the factors in multiplication problems.

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24 times 15 would give you the same product as 15 times 24.

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But please don't take my word for it, you should test it out on your own. And thank you for watching this lesson.