gayanep wrote:

Hi,

I was just going through the 1st book of the

Manhattan Gmat guides (Fractions, Decimals and Percents, 5th Edition) and on page 58 where they are discussing percent changes, they say "You can save time by noticing that 720 and 1800 are both divisible by 360" (referring to a fraction 720/1800- although the context doesnt really matter here). My question is,

how do you NOTICE something like this? What is the trick to being able to recognize factors/multiples in large numbers in order to reduce fractions quickly?

Hope my question is clear.

Thank you all!

Hi gayanep,

You see 720/1800 is actually still easy....can be reduced to 72/180 or 72 is 40% of 180... 40% can be written (2/5)*100

Note that 72(18*4) is a multiple of 18 so knowing your tables till 20 will definitely help to begin with. You should also if possible memorize fractions till 20...

Check out these posts.You should find them helpful

what-arithmetic-should-i-memorize-80128.html#p602003new-to-the-math-forum-please-read-this-first-140445.htmlhow-to-improve-your-quant-from-q44-to-q50-141670.htmlDo use Search options to get more out of GC...

See you around

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