Advanced Topics · Lesson 11 · Practice
Practice: Cross-Borders
Every quiz type from this lesson. Start at difficulty 1 and work up; correct answers build your streak, and after a few attempts this page points you at your weakest quiz.
Order the borders
Difficulty 1
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Arrange the borders of 1111 in increasing length. Pick each in order.
Difficulty 2
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Arrange the borders of 111011111 in increasing length. Pick each in order.
Difficulty 3
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Arrange the borders of 00010100100 in increasing length. Pick each in order.
Difficulty 4
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Arrange the borders of 0100100000001001000 in increasing length. Pick each in order.
Classify words
Difficulty 1
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Classify each word: unbordered or bordered?
Difficulty 2
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Classify each word: unbordered or bordered?
Difficulty 3
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Classify each word: unbordered or bordered?
Difficulty 4
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Classify each word: unbordered or bordered?
Select the shortest border
Difficulty 1
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Select the shortest border of 11101 on the word below.
Difficulty 2
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Select the shortest border of 111101 on the word below.
Difficulty 3
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Select the shortest border of 010111101001 on the word below.
Difficulty 4
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Select the shortest border of 0101000100110101 on the word below.
Count pairs with no cross-border
Difficulty 1
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How many ordered pairs (u, v) of length 5 over a 2-letter
alphabet have no cross-border?
Difficulty 2
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How many ordered pairs (u, v) of length 7 over a 2-letter
alphabet have no cross-border?
Difficulty 3
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How many ordered pairs (u, v) of length 5 over a 3-letter
alphabet have no cross-border?
Difficulty 4
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How many ordered pairs (u, v) of length 11 over a 3-letter
alphabet have no cross-border?