The college students went to the camp. They were dancing near the campfire when suddenly rains fall down and campfire got extinguished.
One of the student Eden has a torch and some batteries. He realized that he got a total of 8 batteries out of which 4 are charged and 4 are not. Eden doesn't know which batteries are charged and which are not.
What is the least number of attempts Eden needs to light up the torch?
7
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
