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Welcome to Brainfuse
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In this lesson, will review how to subtract integers. Let's dissect a simple problem to make sure we understand what it is asking.
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We have 3
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minus
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2.
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In this problem,
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3 is called the minuend that's the number you start off with
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and I'll mark it on the number line.
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And 2 is called the subtrahend that's the number that is taken away
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From the minuend.
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And the answer
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Is the difference
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That is, what you have left.
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Let's say I won 3 tickets to a show. I give away 2 of those tickets to my friends, the difference
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Is what I'd have left. I have 1 ticket, which is all I need.
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But let's look at how this problem works on the number line. When I set this line up, I start at the point
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0 and you can see that the line shows the integers from 0 to 10. When we added 3
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And 2 in the lesson on addition, we moved to the right.
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Where the values of the numbers increase
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When we subtract 2 from 3, in which direction should we move?
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We move to the left
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We move to the left
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Starting at 3
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I move to 2
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Then 1
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So the number line shows me that 3 minus 2 equals 1.
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Oops, I broke the color code
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There we go. Let's use that skill to try 3 more subtraction problems
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Let's find the difference between 25 and 2.
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Okay, 25 is our minuend
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And 2 is the subtrahend. Notice again I lined up the digits in the ones place and
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the lonely digit in the tens place. And again, I start in the ones place on the right with 5 minus 2
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5 minus 2 is 3
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I then see a 2 in the tens place, but no other number. So there's nothing to subtract from that 2
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Then I can write the 2 tens
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Down here. We have 2 tens and 3 ones which equals 23
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Okay, let's try a more challenging one.
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This time we have 2 double digit numbers, 93
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minus 25, so those are the digits in the tens column
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Here at the digits in the ones column.
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So, I go to the ones place and each number and I see a 3 and a 5.
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But there's a problem, because 3 is the minuend and the 5 is the subtrahend, but
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3 is less than 5
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So how can I subtract these numbers? What you can do now is borrow some numbers from the other
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column to make this happen. I'm going to take 1 ten away from the 9 tens in 93
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That makes 9 tens
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8 tens instead.
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And my 1 ten I can add to the 3 ones here, so that is 1 ten plus 3 ones, that's 13.
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So I now have 13 minus 5, which is doable.
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If I subtract 5 numbers from 13 that gives me 12, 11, 10, 9, 8.
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13 minus 5 is 8
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Let's move to the tens column, here we have 8 minus 2.
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8 minus 2 is 6, so the difference between
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93 and 25
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Is 68
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Or 6 tens and 8 ones
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Now, there is one number that will not let you borrow anything from it, can you guess which one that is?
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We will find it in the next problem.
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Alright, so here we have 303 minus 125
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Now again, we start in the ones place and see the 3 minus 5.
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Since the 3 is still less than 5, I need to borrow a value from the tens column. But when I go there,
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there's a 0 in the tens place and 0 has no value, so
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You can just move on to the hundreds column here we see 3 hundreds. We take 1
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hundred away from that, making it 2 hundreds
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And give that hundred to the 0
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Now that 0 is equal to 10 tens, but not for long. To give the 3 a greater value,
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We need to take 1 ten away from this number and give it to the 3. We do that.
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Our
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10 tens becomes 9 tens
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And we are able to
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Add 1 ten to the 3.
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Again, making this 13 minus 5, which is 8.
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And moving to the tens column we have it 9 minus 2 is 7, and
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Moving to the hundreds column 2 minus 1 is 1.
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The difference between 303 and 125 is 178. Notice that I only borrowed values from digits in the minuend.
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In this case: 303. The subtrahend needs to be left on its own. There is an easy way to
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check these problems since subtraction is the inverse operation of addition. If you take 178
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An add the subtrahend to it,
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Add 125, then their sum should equal
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The minuend. So that is the difference
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plus the subtrahend
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should equal the minuend
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Let's see if that actually happens.
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So, 8 plus 5 equals 13, we carry the 1
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And 7 plus 2 is 9 plus 1 is 10 or it's a zero in the tens column
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and carry the one to the hundreds column. 1 plus 1 is 2 plus 1 is 3
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And yes, the sum is 303.
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This gives you a way to make sure that you're correct thank you for watching this lesson.