Math Is Fun Forum

graciecc12

Member

Registered: 2008-03-20

Posts: 2

easy fractions comparing

Here is a SUPER easy way to compare fractions rather than finding common denominators and all of that stuff.  Lets say i want to compare 7/9 and 4/5. Well, if i could write the fraction right on here, seven would be on top. You take your FIRST numerator and multiply it by you SECOND denominator. You write the product BELOW the FIRST fraction. Then, you take the SECOND numerator and multiply it by the FIRST denominator. Write this product BELOW your SECOND fraction. Then, all you have to do is compare these numbers.

7/9     4/5

7*5=35
4*9=36.

35<36.

Therefore:
7/9<4/5.
Pretty easy, huh? Try it with any set of fractions. My fifth grade math teacher taught my class that a few days ago.

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mathsyperson

Moderator

Registered: 2005-06-22

Posts: 4,900

Re: easy fractions comparing

That's a very nice, easy method (as long as your numbers are manageable).

If you're interested, what you're actually doing is writing them as equivalent fractions with a common denominator and then cancelling the denominators out.

You have 7/9 and 4/5.
These are equivalent to 35/45 and 36/45 respectively. Now ignore the denominators and you see that the second fraction is bigger.

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Why did the vector cross the road?
It wanted to be normal.

sir_afezi

Member

Registered: 2008-03-20

Posts: 1

Re: easy fractions comparing

thats really work to me..