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Maths efficiency in case

case math mental math
New answer on Jan 16, 2023
5 Answers
479 Views
Anonymous A asked on Jan 14, 2023

I came across a case where I had to do the following calculations:

- 6090 / 12

- 29600 / 12

- 20181 / 12

I know I can do this with long division but I feel it takes too long. Is there a more efficient maths formula/technique to solve these?

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Cristian
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Content Creator
updated an answer on Jan 16, 2023
#1 rated MBB & McKinsey Coach

Hi there, 

What you can always do is to divide the denominator further. 

Basically:

6090 / 12 = 6090 / 4 * 3 = 6090 / 2 * 2 * 3 = 3045 / 2 * 3 = 1015 / 2 = 507.5.

Happy to share a few additional resources on improving maths speed - reach out.

Best,

Cristian

(edited)

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Hagen
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replied on Jan 15, 2023
#1 Bain coach | >95% success rate | interviewer for 8+ years | mentor and coach for 7+ years

Hi there,

I think this is an interesting question that may be relevant for many people. I would be happy to share my thoughts on it:

  • Yes, there is a more efficient way to solve these calculations. The problem you are solving is dividing a number by 12. Instead of using long division, you can use a shortcut to divide by 12 by simply dividing the number by 10 and then by 1.2.
  • Here's how you can use this shortcut to solve the calculations you provided:
    • 6090 / 12 = 6090 / 10 / 1.2 = 609 / 1.2 = 507.5
    • 29600 / 12 = 29600 / 10 / 1.2 = 2960 / 1.2 = 2466.67
    • 20181 / 12 = 20181 / 10 / 1.2 = 2018.1 / 1.2 = 1681.75
  • In conclusion, you can use the shortcut of dividing the number by 10 and then by 1.2 to quickly divide by 12. This is a more efficient and faster way than using long division to solve these calculations.

If you would like a more detailed discussion on how to address your specific situation, please don't hesitate to contact me directly.

Best,

Hagen

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Florian
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replied on Jan 16, 2023
Highest-rated McKinsey coach (ratings, offers, sessions) | 500+ offers | Author of The 1% & Consulting Career Secrets

Hi there,

If this pops up in a case question, my first question would instantly be if the interviewer expects an exact answer or if you can round the numbers (which 99% of interviewers will agree too).

Then change it to 6000 / 12, which is 500. Fairly simple and takes less than 10 seconds.

Cheers,

Florian

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Ian
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replied on Jan 16, 2023
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

You should round here.

6090 / 12 is essentially 6000 / 12.

Which is 3000 / 6

Which 1500 / 3

Which is 500

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Pedro
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replied on Jan 15, 2023
30% off in March 2024 | Bain | EY-Parthenon | Roland Berger | Market Sizing | DARDEN MBA

Yes, just round the numbers. No one will ask you to calculate the exact number. We're looking for analysts who can use calculation tools, not human calculators.

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