Analysis and Approaches for IBDP Maths Ebook 1 | Página 239

77
Paper 1 Section A – Probability with two-way tables
Front Page
Example
There are 25 students in a classroom, and each student plays only one sport. The table
below gives their sport and gender.
Basketball Football Badminton
Male 6 7 2
Female 5 3 2
(a)
(b)
One student is selected at random.
(i)
Calculate the probability that the student is a female or is a basketball
player.
(ii) Given that the student selected is male, calculate the probability that the
student does not play football.
[4]
Two students are selected at random. Calculate the probability that neither student
plays badminton.
[3]
18
Solution
(a) (i) The required probability
6 � 5 � 3�
2
� (A1) for correct formula
25
16
� A1 N2
25
(ii) The required probability
6�
2
� (A1) for correct formula
6 � 7 � 2
8
� A1 N2
15
(b)
The required probability
� 6 � 5 � 7 � 3 �� 6 � 5 � 7 � 3�1�
� � �� �
� 25 �� 25 �1
�
A2
� 21 �� 20 �
� � �� �
� 25 �� 24 �
7
�
10
A1 N1
[4]
[3]
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