Puzzle 8: There are 10 boxes of apples. Each apple in the boxes weights 1 pound, except that one of the boxes contains bad apples, which weights 0.9 pound each. You are given a digital weight (not a scale), and you can take apples out of the boxes. What is the minimum time of weighs to find out which box has bad apples?
Show Solution
Solution: In three division
a) Take one apple from each box weight 5 on each side.
b) From five divide 2-2-1
c) Then weigh again 2 if required.
Advanced Solution: Using scale one time only.
a) Take 1 apple from box 1, 2 apples from box 2 ... 10 apples from box 10
b) Put all on scale, say it shows XX.Y pounds
c) Look at Y (fractional part).
d) if it's 0, it's box 10
1 - box 9
2 - box 8
...
9 - box 1
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