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1. Compute the following values. Here the operation mod n is the remainder opera

ID: 2902748 • Letter: 1

Question

1. Compute the following values. Here the operation mod n is the remainder operation as defined in the book. Recall that 0 <= r < n where r represents the remainder and m represents the modulus.
a) 15 mod 7=______
b) 10 mod 7=______
c) 150 mod 7 = _____
d) 2^6 mod 5=_____
e) 2^4 mod 5=_____
f) 2^10 mod 5=_____
g) 100 mod 3=____
h)13 mod 3=_____
i) 1300 mod 3=____
j) If p mod 7= 4 and q mod 7= 3, then p*q mod 7 is in what equivalence class of congruence mod 7?

2. Compute the following values. Here the operation mod n is the remainder operation as defined in the book. Recall that 0 <= r < n where r represents the remainder and m represents the modulus.

a) 50 mod 7= ______    and 15 mod 7 = ________  
b) 10 mod 7= ______ and 3 mod 7= _________   note that 50=10*5 and 15=3*5
c) 24 mod 11= _____ and 68 mod 11=________
d) 6 mod 11= _____ and 17 mod 11=________   note that 24=6*4 and 68=17*4
e) 12 mod 5=______ and 27 mod 5= ________
f) 4 mod 5=______ and 9 mod 5 = ________   note that 12=4*3 and 27=9*3
g) 30 mod 3=______ and 45 mod 3=________
h) 6 mod 3=______ and 9 mod 3= _________   note that 30=6*5 and 45=9*5
i) 52 mod 7=_______   and 80 mod 7=________
j) 13 mod 7=_______   and 20 mod 7=________   note that 52=13*4 and 80=20*4

3. The computations in question 2 are organized in 5 pairs a-b, c-d, e-f, g-h and i-j. Using these pairs as observation, which of the following statements appear to be true. Assume n represents the modulus, k represents a common factor and a,b are integers.
a) True or False If n and k are relatively prime and if ak mod n=bk mod n, then a=b.
b) True or False If n and k are relatively prime and if ak mod n=bk mod n, then ak=bk.
c) True or False If n and k are relatively prime and if ak mod n=bk mod n, then a mod n=b mod n.
d) True or False If n and k are relatively prime and if ak mod n=bk mod n, then a mod n=ak mod n.

4. See page 128 problem 22 for information relating to this question. Guess and check is an acceptable technique for these problems.

5. Find an integer value for x if possible, that makes the following statements true.

6. Using the computations in problem 5 as examples, find an integer value for x if possible, that makes the following statements true. (k represents a nonzero integer.)

1. Compute the following values. Here the operation mod n is the remainder operation as defined in the book. Recall that 0

Explanation / Answer

1.   a) 15 mod 7= 1

b) 10 mod 7=3
c) 150 mod 7 = 3
d) 2^6 mod 5=4
e) 2^4 mod 5=1
f) 2^10 mod 5=4
g) 100 mod 3=1
h)13 mod 3=1
i) 1300 mod 3=1

j) If p mod 7= 4 then p=7*N +4 and q mod 7= 3, then q=7*N +3

j) If p mod 7= 4 then p=7*N +4 and q mod 7= 3, then q=7*N +3

p*q mod 7 =5

2. a 1

   b. 3

   c. 2

d. 6

e. 2

   f.   4

g. 0

h. 0

i. 3

j. 6

3. a. false

   b. false

   c. true

   d. false

4. a. 2x= 3mod8

          2x = 8k+3

        x = 4k+1.5 so x will not be integer

b. 5x = 6 mod8

       5x = 8k+6

        x = 1.6k+1.2 at k=3 so x=6

5. a. 6

     b. 0

     c. 3

      d. 6

      e. 0

      f. 3

     g. 3

     h. 0

6. a. x=0 if k = 1

    b. x=6 if k=6