## Comparing Fractions 2

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Use < , > , = to compare the two fractions 21/28
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and 6/9. So there is a buch of ways to do this.
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The easiest way is if they have the same
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denominator, we can compare the numerators.
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Unfortunately we do not have the same denominators
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So we could do is we could find common denominators
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for both the fractions and convert both the fractions
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to have common denominators and compare the
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numerators.Or even more simply we can
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simplify them first and then try do it.
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So 21/28 , they are both divisibley by 7.
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Let us divide the numerator & denominator by 7
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21 divide by 7 & 28 divide by 7.
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Since we are dividing both by 7, we are not changing
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the value of the fraction 21 ÷ 7 = 3
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28 ÷ 7 = 4.
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So 21/28 = 3/4.
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Lets us do the same thing for 6/9
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6 & 9 are both divisible by 3
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So lets divide both 6 & 9 by 3
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6 ÷ 3 = 2
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9 ÷ 3 = 3
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21/28 = 3/4
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6/9 = 2/3
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So we really can compare 3/4 & 2/3.
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The real benefit of doing this, it is easy to find
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common denominators for this than 28 &9
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which means we need to multiply larger numbers
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here we have smaller numbers.
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the common denominator of 3/4 & 2/3 is the LCM
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of 4 & 3.
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4 & 3 does not share any prime factors with each other
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so LCM of 4 & 3 is the product of the 2 numbers
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3/4 = /12
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2/3 = /12
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I got 12 by multiplying 3 & 4 as they have no
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common factors. another way to think is
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prime factorization of 4 = 2x2
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3 is already a prime number, so prime factorization
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of 3 is 3.
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The number that has all prime factors of 4 & 3 is 2,2 & 3
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2x2x3 = 12.This is how we get LCM
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to get from 4 to 12 ,you got to multiply 3
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We multiply denominator by 3 to get 12
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We need to multiply the numerator by 3
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3 x 3 = 9
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To get from 3 to 12, we multiply denominator by 4
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We also have to multiply numerator by 4
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4 x 2 = 8
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21/28 = 3/4 = 9/12
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6/9 = 2/3 = 8/12
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Which of these is a greater fraction.
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Since we have common denominator, we need to
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look at the numerator. We know 9 > 8
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So, 21/28 > 6/9
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And we are done.
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Another way to do is
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we need not simply it. just do it for fun.
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If we did not simplify it 21/28 & 6/9
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LCM of 28 & 9
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prime factorization of 28 = 2x2x7
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Prime factorization of 9 = 3x3
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The LCM of 28 & 9 must contain 2x2x3x3x7
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which is esentially 28x9 = 252
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The common denominator is going to be 252
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To go from 28 to 252 we had to
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multiply 28 by 9 ; 28 x 9
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So we also have to multiply numerator by 9
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21x9 = 189
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To go from 9 to 252
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we need to multiply by 28.
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So we need to multiply numerator by 28
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So 6x28 = 168
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Now we have a common denominator here
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and we can compare the numerator.
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189 > 168
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So 21/28 > 6/9
Title:
Comparing Fractions 2
Description:

u2_l1_t5_we2 Comparing Fractions

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Video Language:
English
Duration:
07:08
 Vetrivel Foundation edited английски език subtitles for Comparing Fractions 2 raji.krithi added a translation

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