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Welcome to Brainfuse!
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In this lesson we'll review how to divide fractions
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The division problem on screen is written in two different ways
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On the left we have fractional notation it's written like a fraction we have the numerator 2/5
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Over the denominator 3/5
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And another way to write this problem is on the right side of the screen where we have
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2/5 divided by 3/5
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Using the traditional sign for division
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To figure out what's happening when we divide this fractional notation
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May be the best example to use for this lesson
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So we have two fifths
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over 3/5
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To make this problem simpler I do not want to work with this denominator I want to find a way to cancel it out
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We can do that by multiplying the fraction in the denominator by some fraction
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That will result in a product of 1
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So which fraction would do that?
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That fraction is called the reciprocal
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And to find the reciprocal
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All you need to do
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Is
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Flip the numerator and the denominator
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If you did that, 5 would become the numerator and
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3 would become the denominator
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And so 3 times 5 equals 15
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5 times 3 equals 15
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Set this result would equal one
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So how can we get away with doing this? The only way we can
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Is if we also
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Multiply 2/5
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By 5/3
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Okay, so that equals again 5 x 3 in the denominator we have
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15
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And
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2 times 5 gives us 10
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So we're now left with
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10/15
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I'll rewrite it over here or since
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It's crowded
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We're left with
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10
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15
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Over 1
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So since it's over one we can just rewrite that as 10/15
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And can we simplify this any further?
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Well 10 and 15 both have a
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Common factor they have 5 as a factor
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So let's divide both sides again the numerator and denominator
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By 5
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10 divided by 5 is 2
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And 15 divided by 5 is 3
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So our final answer
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Is 2/3
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Let's try one with more challenging numbers just to make sure you have the skill down
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So we'll use some improper fractions
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In the spirit of division we can divide the screen and use the right side
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I'll just delete this so it's not as confusing
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So this time let's try
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11
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Over 2
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divided by
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9 / 7
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Okay so I do not want to work with that denominator so what can I multiply
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That by to have a result of one?
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That would be its reciprocal
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7/9. Again, we just flip the numerator and denominator
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But whatever I do to the denominator I need to do to the numerator
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So that leaves us with
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Let's see
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9 times 7 is equal to 63
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And 7 times 9 is surprisingly equal to 63, so 63 over 63 equals 1
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And up top of the numerator
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We have 11 x 7 is 77
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And 2 times 9 is 18 so that gives us 77/18 over 1
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And since it's over one that's equal to 77/18
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For some extra practice with improper fractions let's go ahead and convert that
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To a mixed number
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18 goes into 77 four times
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18 x 4 is 72 so 77-72 is 5
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So we're left with 4 5/18 as our answer
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Now it's your turn to practice dividing fractions and thank you for watching this lesson.