Practice Addition And Subtraction Rules (7.4.3.1) - Lecture

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6 sample questions

Question 1.
Calculate 12 mod 5.
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Think about how many times `5` fits into `12`.
Question 2.
What is 9 mod 4?
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Consider the remainder when you divide `9` by `4`.
3Question 3.
If 8 ≡ x (mod 5) and x = 3, what is true?
- True
- False
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Consider how both numbers interact with `5`.
4Question 4.
In modular arithmetic, a + b (mod N) is equivalent to:
- a + b
- a mod N + b mod N
- a + b + N
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Revisit how remainders are calculated.
Question 5.
Explore the implications of 15 ac ≡ 5 bc (mod 10). Under what conditions can 'c' be cancelled from both sides?
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Consider when numbers become zero mod 10.
Question 6.
Demonstrate the failure of division in modular arithmetic by finding values of a and b such that a/b (mod 8) yields an invalid conclusion.
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Explore values that don’t yield clean divisions.

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