comparing fractions
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comparing fractions
In NFER 11c q14 you are asked to find the largest out of 7/8 3/4 6/9 10/12 3/5. I can not see a common denominatorfor for all these numbers, and converting all of them to decimal could be time consuming in an exam. Has anyone has a really quick way to compare these fractions?
Re: comparing fractions
System I used with DD. Will vary slightly depending on numbers and whether you are, for example, after biggest or smallest.ggd wrote:In NFER 11c q14 you are asked to find the largest out of 7/8 3/4 6/9 10/12 3/5. I can not see a common denominatorfor for all these numbers, and converting all of them to decimal could be time consuming in an exam. Has anyone has a really quick way to compare these fractions?
For the numbers you give.
Eliminate the smallest numbers.
Do this by looking for those numbers bigger than, say 1/2 or 3/4. 3/4 would seem to be the better choice. 7/8 and 10/12 are obviously bigger than 3/4. Straightaway down to two numbers.
After the biggest of the remaining two numbers.
Both numbers are smaller than 1, so compare and determine how close.
7/8 is 1/8 away, and 10/12 is 2/12 or 1/6 away. 1/8 is the smallest number, so 7/8 is closest to 1 and therefore biggest number.
The method looks a bit long-winded, but in practice, providing child has a reasonable grasp of equivalent fractions, only takes a few seconds, and does not involve any writing down.
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Re: comparing fractions
Higgd wrote:In NFER 11c q14 you are asked to find the largest out of 7/8 3/4 6/9 10/12 3/5. I can not see a common denominatorfor for all these numbers, and converting all of them to decimal could be time consuming in an exam. Has anyone has a really quick way to compare these fractions?
The common denominator is 360
Therefore
7/8 = 315/360
3/4 = 270/360
6/9 = 240/360
10/12 = 300/360
3/5 = 216/360
Hence the largest is 315/360 i.e 7/8
Hope this helps
yes, I was thinking some elimination would help matters with the cross-comparing. No point even including ones you know aren't in the mix, and then, finding a common denominator which is small enough to be of practical use is far more likely.
EDIT - actually posted before Essexmum's but the machine is hanging here and took a long time to bother sending it - wasn't meaning a dig at 360 being a "useful" common denominator!
EDIT - actually posted before Essexmum's but the machine is hanging here and took a long time to bother sending it - wasn't meaning a dig at 360 being a "useful" common denominator!