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Approach to increasing margin calculation

Can someone please help me with the best logic to approach this question? The answer I am arriving at isn't making sense to me as it is over 100%. A firm with a 90% margin is planning to increase revenue by 10% and decrease cost by 10%, what will its new margin be? 

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Top answer
Moritz
Coach
on Jul 05, 2022
ex-McKinsey EM & Interviewer | 7/8 offer rate for 4+ sessions | High impact sessions + FREE materials & exercises

The answer is ~91.8%, corresponding to ~1.8% margin increase.

Please consider the following, where r is revenue, c is cost, and x is the new margin:

  • Current: (r - c) / r = 90% → (100 - 10) / 100 = 90%
  • Proposed: (r*1.1 - c*0.9) / (r*1.1) = x → (100*1.1 - 10*0.9) / (100*1.1) = (110-9) / (110) = 91.8%

Hope this helps!

Hani
Coach
on Jul 05, 2022
Associate and All-star Interviewer at OW | Ex-S& | 5+ years in the Middle East |300+ Interviews | INSEAD MBA

Hi there,

The best way to solve this kind of problem is to use numerical examples:

Let's assume the following:

  • Initial Revenue = 100
  • Initial Cost = 10
  • Initial Margin = (Revenue - Cost) / Revenue = (100-10)/100 = 90%

This is your current state now the company wants to increase revenues by 10% and reduce costs by 10% so your new values would be the following:

  • New Revenue = Initial Revenue * 1.1 (or * 110% to show increase of 10%) = 100 *1.1 = 110
  • New Cost = Initial Cost * 0.9  (or 90% to show decrease of 10%) = 10 * 0.9 = 9
  • New Margin = (New Revenue - New Cost) / New Revenue = (110 - 9)/110 = ~92% or you can integrate the initial values but since it was already calculated no need to complicate the math 

If the firm manages to increase revenues by 10% and decrease costs by 10% it will have an incremental 2% in the margin with a net margin of 92%  

Hope this was helpful!

Ian
Coach
on Jul 06, 2022
Top US BCG / MBB Coach - 5,000 sessions |Tech, Platinion, Big 4 | 9/9 personal interviews passed | 95% candidate success

Hi there,

Hani and Mortiz are exactly right!

Make sure that you fully understand the major math concepts (Margin, Markup, ROI, Breakeven, NPV,  etc.) and how to apply them in multiple scenarios!

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