Shortcuts to the math problems tests

Shortcuts to the math problems tests
Recent activity on Apr 26, 2019
3 Answers
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Anonymous A asked on Apr 10, 2019

Can somebody explain to me the shortcut to the question below? To get to the answer I have to make 17 o[perations in 80 seconds... not possible, there should be a shortcut to the solution. (the right answer is D).

Is there a list of shortcuts that usually can be used?

SHL shortcuts

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updated an answer on Apr 10, 2019
#1 Coach for Sessions (4.000+) | 1.500+ 5-Star Reviews | Proven Success (➡ | Ex BCG | 10Y+ Coaching

Hi Anonymous,

first of all you can exclude the information on 9 hours day/ 7 days, rather focus on the revenues per minute.

Assuming that by “cost” they actually meant “price”, you can start finding the revenues per minute of the monitor produced. You could also calculate the revenues per hour, but that would take longer to compute and with bigger numbers:

  • A: 175/15=11.67
  • B: 188/18=10.44
  • C: 145/13=11.15
  • D: 198/20=9.9
  • E: 170/17=10

You can then calculate the average revenue per monitor sold:

  • A: 75%*11.67
  • B: 73%*10.44
  • C: 84%*11.15
  • D: 95%*9.9
  • E: 81%*10

You don’t have to calculate B because it is worse than A, and you don’t have to calculate E since it is worse than C

  • A: 75%*11.67=8.75
  • C: 84%*11.15=9,36
  • D: 95%*9.9=9,41

Thus the best option is D.

This still requires 8 computations with two digits after comma, and it is unlikely you will be able to do all in 80 seconds – more likely, at least 3 minutes. But 80 seconds is the average amount of time spent per question, thus you probably spent less time on other questions and can dedicate more time for this.

Hope this helps,



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replied on Apr 26, 2019
BCG | Kellogg MBA |82% Success rate| 450+ case interview| 5+ year consulting | 30+ projects in ~10 countries

It looks like our experts already provided the best solutions.

In my opinion, this question does not look like a good problem for consulting interviews as it looks like not carefully designed.

First, it should be revenue but not cost.

Second, it requires detailed calculation as option C and D is very close to each other. I never have seen such a requirement in quality consulting materials.



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Arnaud replied on Apr 10, 2019

Hi Anonymous,

Hard to spot a clear shortcut, but what I can see is the following:

  1. Models B, D and E seem to have a cost / min (Cost per monitor / Time to manufacture) very close to 10 $/min (when rounding up) When you apply the % of monitors sold to this, you find that Monitor D is the best line of the three (95%)
  2. Models A and C are closer to 11-12 $/min, but when applying the % of monitor sold, even when considering the higher bracket 12$/min, they're still below D
  3. Thus D is the answer

I guess the trick is to spot the 3 monitors with similar cost per monitor / min and use this as a starting point.

I'd be interested if anyone finds another quicker way to do this.

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Eugene on Apr 10, 2019

Thanks, Arnud. That's interesting observation.

Eugene on Apr 10, 2019

And SHL... when they use a word "cost" - for me it's a cost of manufacturing, but not the sale price.

Arnaud on Apr 10, 2019

I assumed cost referred to sales price - otherwise you have no data to estimate any revenue

Francesco gave the best answer


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