Problem 6 · 2016 Math Kangaroo
Easy
Logic & Word Problems
careful-counting
Maria wants there to be a knife to the right of every plate and a fork to the left of it. To get the right order she always swaps one fork with one knife. What is the minimum number of swaps necessary?
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Answer: B — 2
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Hint 1 of 2
Mark every place where a fork is wrongly on the right or a knife wrongly on the left.
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Hint 2 of 2
One swap fixes one wrong fork together with one wrong knife at the same time.
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Approach: count the misplaced utensils, then pair them up
- Check each place setting and mark every fork that is wrongly on the right and every knife wrongly on the left.
- There are 2 such wrong utensils, and one swap trades a wrong fork for a wrong knife, fixing both at the same time.
- So the minimum number of swaps is 2, choice (B).
Mark:
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