Problem 9 · 2018 Math Kangaroo
Medium
Spatial & Visual Reasoning
careful-counting
Charles cuts one rope into 3 pieces that are all the same length. He ties 1 knot in the first piece, 2 knots in the next, and 3 knots in the last. Then he lays the three pieces down in any order. Which picture does he see?
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Answer: B
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Hint 1 of 3
Two things must be true in the right picture — about how many knots AND about the rope lengths.
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Hint 2 of 3
Count knots: the three pieces should show 1 knot, 2 knots, and 3 knots — one of each.
Still stuck? Show hint 3 →
Hint 3 of 3
Don't forget the pieces were cut to be the SAME length, so all three ropes must look equally long.
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Approach: check both the knot counts and that the three ropes are equal length
- The three pieces must show one rope with 1 knot, one with 2 knots, and one with 3 knots.
- But the pieces were cut to be the same length, so all three ropes must also be equally long.
- Only option B has both: ropes of 1, 2 and 3 knots that are all the same length.
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