2.12: Alternating character codes and netball team
(a)[3]
A 5-character code is to be formed from the 13 characters shown below. Each character may be used once only in any code.
Letters: A, B, C, D, E, F
Numbers: 1, 2, 3, 4, 5, 6, 7
Find the number of different codes in which no two letters follow each other and no two numbers follow each other.
(b)[3]
A netball team of 7 players is to be chosen from 10 girls. 3 of these 10 girls are sisters. Find the number of different ways the team can be chosen if the team does not contain all 3 sisters.