Part of case questions: How many batteries can be saved

Big 4 case question
Recent activity on Aug 11, 2018
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Anonymous A asked on Aug 10, 2018

Recent case interview, I was asked to calculate how many battery our client's battery can save for their customers.

Background: client manufactures battery for forklifts. Their battery has outstanding quality and duration lifetime. The battery can be continuously used for 12 hours and needs to be charged for 8 hours. Their competitors' battery can be used for 10 hours and needs to be charged for 10 hours. Question: how many batteries the customers can save by using our client's battery.

There are definitely other factors I've examined e.g. extra energy saving by using our client's battery. However, I was stuck in the calculation of the above question. Could anyone help me:
(1) figure out the CORRECT calculation?
(2) suggest some cases either from preplounge or casebooks where I can practise on this type of math?

MBB interviews ahead. needs to improve it.

Thank you!

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updated an answer on Aug 11, 2018
McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School


There is something that you are missing here - the timeframe!

You should always ask the timeframe in your clarifying questions. Every objective should have a clear metric (number of batteries saved in this case) and a time frame.

For every 20 hours cycle, you'll be saving 2/10 = 1/5 of a current battery time. Plus you may have additional savings if the charging time requires some extra battery power. Multiply the total savings by the time frame and you'll get the number of batteries saved.



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McKinsey / Accenture Alum / Got all BIG3 offers / Harvard Business School
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