perplexus.info :: Weights and Scales : Finding Good Batteries

Finding Good Batteries (Posted on 2013-11-11)

My remote control needs two new batteries, but when I went to get replacements I found that the four good batteries got mixed in with four bad batteries. The only means of determining if the batteries are good is to put two into the remote and see if it works. The remote works with two good batteries and is unresponsive if I have at least one bad battery in it.

What is the minimum number of tries I need to guarantee that I get two good batteries?

See The Solution Submitted by Brian Smith

Rating: 4.5000 (2 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)

re: my solution

| Comment 5 of 8 |

(In reply to my solution by Charlie)

Apparently, I've answered a wrong question ( trying the batteries two-by-two what is the worst case?) and failed address the real issue.

Your approach is a correct one , but the answer( to puzzle's questi

i.e. What is the minimum number of tries I need to guarantee...etc is 7 , not eight : you were requested to identify a pair of good batteries, not to immediately use them.

PS I - THere is a typo in the title - don't know how to edit it...

PS II- Meanwhile I have posted a shorter procedure.

Edited on November 12, 2013, 4:23 am

Posted by Ady TZIDON on 2013-11-12 02:03:41

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