Analysis and Approaches for IBDP Maths Ebook 2 | Page 230

Your Practice Set – Analysis and Approaches for IBDP Mathematics
71
Paper 2 Section A – Permutations
Example
In an interview, four male interviewees and five female interviewees are asked to sit on a
row of nine seats outside the interview room.
(a)
(b)
(c)
Find the number of ways if the interviewees of the same gender must sit together.
[3]
Find the number of ways if male interviewees must sit together.
[3]
Find the number of ways if male interviewees must not sit together.
[2]
Solution
(a)
(b)
(c)
The number of ways
� 4! �5! � 2
(A2) for correct factorials
� 5760
A1
The number of ways
�4! � 6!
(A2) for correct factorials
� 17280
A1
The number of ways
6
� P 4
� 5!
(A1) for correct factorial
� 43200
A1
[3]
[3]
[2]
Exercise 71
1. Consider five English letters M, E, R, C and I. Find the number of different words with
five letters that can be made from these letters if
(a)
(b)
(c)
there is no restriction,
the letters M and E must stick with each other,
the first letter must not be a vowel.
[2]
[3]
[3]
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