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