Problem of the Day
A new programming or logic puzzle every Mon-Fri

Battery Test

It's Sunday night and you're sitting on your couch getting ready to watch the latest episode of Game of Thrones when you realize you forgot to watch last week's episode. You're too lazy to get up and change the channel so you're dedicated to using the remote which requires 2 batteries.

Unfortunately the remote is missing batteries but the battery drawer is within arms reach. You reach in and find a note that says "4 of these work and 4 of these do not". There are 28 possible combinations but you only have time to try at most 7 combinations of batteries before the spoilers come on. What strategy can you adopt to ensure you can change the channel in time?

Enjoy your weekend!

Permalink: http://problemotd.com/problem/battery-test/

Comments:

  • Daniel - 10 years, 7 months ago

    Split the batteries up into 3 groups of 3, 3, and 2. This will mean that at least one group will have two working batteries.

    Group 1 (A, B, C) Group 2 (J, K, L) Group 3 (Y, Z)

    Test group 1

    AB AC BC

    If none of those work try group 2

    JK JL KL

    If none of those work then

    YZ are your working pair!

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  • Max Burstein - 10 years, 7 months ago

    Nicely done!

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  • Anonymous - 10 years, 6 months ago

    My conclusion was very much the same as Daniel's, but in order to get there, I tried the grouping 4-4 first, then moved on to 3-3-2. Is there a methodical way to get to 3-3-2 combination without trying 4-4 first?

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  • Anonymous - 10 years, 7 months ago

    You call your spouse/child/neighbor over to do it for you.

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