# How Many Spikes Are on the Back of a Hedgehog?

Case Type: estimate/guesstimate; math problem.
Consulting Firm: Oliver Wyman 2nd round job interview.
Industry Coverage: Agriculture, Farming & Aquaculture.

Case Interview Question #00292: How many spikes are there on the back of a hedgehog?

Answering this estimation/guesstimate type of case questions requires answering a number of sub-questions (SQ). To estimate the number of spikes on the back of a hedgehog, the following sub-questions and possible solutions could be used:

1. How do you define the ‘back’ of the hedgehog?
2. What is the area of the back of the hedgehog?
3. How many spikes are there in a specific area?
4. How many spikes are there on the back of the hedgehog?

SQ1: How do you define the ‘back’ of a hedgehog?

• Could define this as the whole area upon which spikes can be found.
• Could be the whole area that is not in contact with the ground.
• Could be an area in a similar proportion to the circumference of the hedgehog (when viewed from above) but of smaller size i.e. the area around it can be described as the sides rather than the back.

Let’s go with the latter option and try to determine the area of that.