Answer Happy

Good example: C(6, 3)C(5,2)= 10 Bad examples: 10 no equation C(6, 3) -C(5,2) no final answer 20-10=10 did not leave combinations intact If the final equation is too complex, introduce variables and break it down into two or more equations. You are encouraged to show additional work to indicate how you derived your equation. 1. (16 points, 4 points each) Let A = {a, b, c, d, e, f, g, h}. Count the number of different strings that meet each of the criteria. a. Strings that are five letters, letters can be repeated. b. Strings that are five letters, letters cannot be repeated. c. Strings that are six letters, either starts with the substring 'ab' or ends with the substring 'gh' or both, letters can be repeated. d. Strings that contain all eight letters exactly once and the letters 'a' and 'b' must be adjacent to each other such as 'feabcdgh' and 'hgdfbaec'.