Hi there,

**Q: I've been doing some practice case math. It takes a long time (10 min or more) to solve one. I'm just wondering how difficult math is in a real case interview?**

In general a math problem during a case should not require 10+ minutes. The reason it takes so long in your case may be because (i) the drills you are using are particularly difficult or (ii) you need to improve your math skills.

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:

**Repeat the question** – sometimes candidates do mistakes answering the wrong question**Ask for time** and **present how you would like to proceed** from a theoretical point of view**Perform the math **and** present the interim steps** to keep the interviewer aligned – don’t just say the final number**Continue with the math** until you find the final answer**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:

**Use correctly the power of 10.** For example, 3.2B / 723M can be written as 3200*10^6 / 732*10^6**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**Keep good notes.** This helps to avoid to forget/misreport numbers**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**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

I definitely agree with Hagen here. There are some cases in these Bschool casebooks that vest so much effort into convoluting complex quantitative knots that it seems to detract from the main focus of learning and improving in cases more generally.