# Best way to convert large fractions to decimals

mental math
New answer on Nov 18, 2019
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E.g. I got stuck on how to do 11/275 during a case

What is the best trick for something like this and many others

Are there any recourses to practice large fractions?

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Hi Anonymous,

assuming you can approximate numbers, in this case you can find what is a relatively small percentage (eg 1%) and see how the number you have to calculate compares to that.

In this case, 1% of 275 is 2.75, which means 2% is 5.5. At this stage, you would probably notice that 11 is therefore exactly 4%.

Best,

Francesco

Hi,
here you can find a detailed approach to solve it in a quick approximated way and in an accurate way: https://www.youtube.com/watch?v=do_IbHId2Os

I recommend you to take a look at the channel, I really appreciate their video on fast math.

Best,
Antonello

Using percetage may be an easy way to covert complex fractions into decimals.

eg. 11/275

275 = 200 + 75

taking 4% of (200 + 75) = 8 + 3 = 11 thus 11/275 = 4% = 0.04

Other way round if you can image breaking the bigger number

11/275 = 11/5 *1/5*1/11 = 1/25 = 4%

There is no hardcoded rule you may use which ever approach comes to your mind and you seem comfortable with it. Hope this is helpful.

Hi,

You should approximate it:

50% of 275 = 135

110 is roughly 40%, thus 11 is 4%

Best

I typically convert the denominator to 100, so in this case for simplicity I would divide denominator by 3, giving me approximately 3.67%. Then I would round up or down depending on whether I have overestimated or underestimated based on the earlier division, so in this case I would round up and say about 3.9%-4%.

But you should ask if rough estimations are fine. 90% of the time your interviewer will be ok with rounding.