7.4.3.2. Multiplication Rules

Try these first

1. 1.

   What is 7 modulo 3?

   Hint

   Subtract multiples of 3 from 7.

2. 2.

   Calculate -10 mod 4.

   Hint

   Think about where -10 lies on a number line mod 4.

3. 3.

   What is the result of 8 mod 5?

   • 3
   • 2
   • 1

   Hint

   Subtract 5 from 8 and see where you land.

4. 4.

   Is -7 congruent to 1 mod 4?

   • True
   • False

   Hint

   Check by calculating the remainders.

5. 5.

   Using the square and multiply method, calculate 2^15 mod 17.

   Hint

   Remember to calculate powers based on binary digits!

6. 6.

   Explain why (a / b) modulo N is not defined generally. Give an example in your explanation.

   Hint

   Consider cases where the numerator is smaller than the denominator.