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Easy way to solve 7M/1.9K

Math problem
New answer on Mar 14, 2023
5 Answers
547 Views
Anonymous A asked on Mar 11, 2023

If you were asked to solve 7M/1.9K, what tricks/shortcuts would you use to find a roughly accurate answer?

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Francesco
Expert
Content Creator
replied on Mar 13, 2023
#1 Coach for Sessions (4.500+) | 1.500+ 5-Star Reviews | Proven Success (➡ interviewoffers.com) | Ex BCG | 10Y+ Coaching

Hi there,

Q: If you were asked to solve 7M/1.9K, what tricks/shortcuts would you use to find a roughly accurate answer?

If you need a “roughly” accurate, you should be able to approximate. I would clarify with the interviewer if that’s an option.

If that’s possible, I would then recommend the following:

  1. Cut the zeros: 7M/1.9k = 7.000/1.9
  2. Approximate 1.9 to 2: 7.000/1.9 ~ 7000/2 = 3.500

Below you can also find some general math tips:

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In terms of how to approach math during the case, this is what I would recommend:

  1. Repeat the question – sometimes candidates do mistakes answering the wrong question
  2. Ask for time and present how you would like to proceed from a theoretical point of view
  3. Perform the math and present the interim steps to keep the interviewer aligned – don’t just say the final number
  4. Continue with the math until you find the final answer
  5. Propose next steps on the basis of the results you found

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In terms of general math tips and avoiding mistakes, I would recommend the following:

  1. Use correctly power of 10. For example, 3.2B / 723M can be written as 3200*10^6 / 732*10^6
  2. Ask if it is fine to approximate. You can ask the interviewer if you can approximate complex math. If allowed, this will help to solve simpler problems. In the previous example, you could get 320*10^7 / 70*10^7
  3. Keep good notes. This helps to avoid to forget/misreport numbers
  4. Divide complex math into multiple simpler steps. For example: (96*39)*10^6 → 96*40 - 96*1 = 100*40 - 4*40 - 96*1 = 4000 – 160 – 100 + 4 → 3744*10^6
  5. Learn main fractions results. You can learn by heart fractions and speed up/simplify the computation - the most useful to know are 1/6 ~ 17%, 1/7 ~ 14%, 1/8 = 12.5%, 1/9 ~ 11%.

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I would also recommend to practice math under pressure - not just math. Many candidates are totally fine doing 67% of 67 in normal conditions, but freeze if asked this suddenly in a case interview.

In order to do so, try always to use a timer with a time constraint when you practice math – this will create pressure and help to replicate the actual conditions of the interview.

Hope this helps,

Francesco

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Hagen
Expert
Content Creator
replied on Mar 13, 2023
#1 recommended coach | >95% success rate | most experience in consulting, interviewing, and coaching

Hi there,

I would be happy to share my thoughts on it:

  • First of all, I would advise you to round to the nearest whole numbers and remove the zeros, leading to 7 / 2 = 3.5. After this, you need to add the appropriate units back to the result, leading to 3.5K.
  • Still, while this might be a calculation that you are expected to perform mentally, it is absolutely fine to perform most calculations in writing.

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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Ian
Expert
Content Creator
replied on Mar 12, 2023
#1 BCG coach | MBB | Tier 2 | Digital, Tech, Platinion | 100% personal success rate (8/8) | 95% candidate success rate

Hi there,

Completely agree with Paul here!

7M/1.9k is the “same” as 7000/2.

You can either write out the zeros or practice knowing what B,M, and K represent.

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Paul
Expert
replied on Mar 12, 2023
PL-level BCG experience (6 years)|Interviewer at BCG| 6/6 personal + 95%+ candidates offer success rate

Hi there,

I would ask the interviewer whether I can approximate 1.9K to 2K, ensuring him that 

1) I would give an evaluation of how much this answer could be “off” 

2) evaluate potential implications (if any) on the answer to the client problem

This could draw IMO 8/10 interviewers to grant permission to approximate.

Then I would do: 7 000 000 / 2 000 → Cut zeros = 7000 / 2 = 3500

As agreed would then proceed to test/ correct answer w/ interviewer

1) How much we are  off: I Increased denominator by 5% (2 vs. 1.9k)→ This means that the answer should be off by -5% (underestimated)

I would therefore tell interviewer the answer is 5% more than 3500 → 10% of 3500 is 350 → 5% = 175 = 3500+175 = 3675

(pretty close - real answer is 3684)

2) Potential implications discussion (if relevant)

 

Hope this help.

Feel free to reach out if you want to deep-dive on similar topics

 

 

 

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Andreas
Expert
replied on Mar 14, 2023
McKinsey EM | Top MBB Coach | >70% Success Rate | Free Introductory Calls

This gives you an accurate enough answer for 95% of cases: 7000/2

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Francesco gave the best answer

Francesco

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