Discussion :: Logical Riddles
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Richard was camping at night near Devon, England. It was very dark there. Richard has a torch that requires two batteries to light up.
He realized that he got a total of 8 batteries out of which 4 are charged and 4 are not. He doesn't know which batteries are charged and which ones are not.
What is the least number of attempts Richard needs to light up the torch?
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Answer : 7
Explanation :
Put batteries into 3 groups: two groups of 3 and one group of 2.
It guarantees at least one of the group has got two working battery
Group of 3 requires 3 attempts to verify if 2 batteries of the group are working (B1+B2, B2+B3, and B1+B3) while the group of 2 requires one attempt (B1+B2)
Total attempts = 3 + 3 + 1 = 7
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