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?

(In reply to my solution by Charlie)

Doesnt it mean 7 tries and not 8. Since when there are 2 bad batteries amond 1,2,3 and 4. If 1&2,1&3,1&4,2&4,3&4 have all not worked meaning atleast one of the batteries is bad 2,3 has to be correct and need not be checked.

Posted by Salil on 2013-11-11 23:46:30