CS1050 HW 9 Answer Key
There are 124 points total over the entire homework.
Section 7.5, p. 513-515, 2, 16, 42
Section 4.1, p. 311, 16, 28
Section 4.2, p. 319, 12, 14
Section 4.3, p. 325, 10, 14
Section 7.5
2) [4 points each]
a. Yes
b. Yes
c. No, not transitive
d. No, not transitive
e. No, not transitive. A and B speak English; B and C speak Spanish, but A doesn't
(nor does C speak English).
16) [10 points]
Yes, the relation is an equivalence relation.
42) [3 points each]
a. No (May not be transitive)
b. Yes
c. No (May not be reflexive)
Section 4.1
16) [10 points]
264 - 254 = 456976 - 390625 = 66351
28) [ 3 points each]
How many strings of eight English letters are there
a. If letters can be repeated.
268
b. If no letters can be repeated.
26*25*24*23*22*21*20*19
c. That start with X, if letters can be repeated.
267
d. That start with X, if no letters can be repeated.
25*24*23*22*21*20*19
e. That start and end with X, if letters can be repeated.
266
f. That start with the letters BO (in that order), if letters can be repeated.
266
g. That start and end with the letters BO (in that order), if letters can be repeated.
264
