Ball

Case Study Prompt

There are 8 balls with same size and look.

One is lighter than the others. How do you find the lighter ball using a balance to weigh just twice?

Case Study Overview

In this BCG case, you’re being asked a creative question meant to test both your analytical and creative thinking processes. These Brainteasers are solved the same way you solve a Market Sizing question – by breaking down the solution into component parts. In Market Sizing cases, you can take a top-down or a bottom-up approach. Which do you think will help you answer this question?

Follow these 4 steps for solving Market Sizing cases:

1. Structure your approach (at least 5 steps is ideal)
2. Make assumptions
3. Do the calculations
4. Get to an insight

This is a beginner level BCG case study question and will prepare you for a first round interview. The qualitative difficulty is 1 out of 4.

BCG Interview Tips

BCG is looking for candidates that are structured and are able to clearly communicate that structure.

When going through the question, make sure that your structure is crystal-clear to you and that you verbalize each part of your process. Make the focus of your presentation how you arrived at our answer.

For this case, make a point to come away with one takeaway or area you can improve.

For out-loud practice with an expert, book an hour with an ex-MBB coach.