Apps. and Interpretation for IBDP Maths Ebook 1 | Page 280

Your Practice Set – Applications and Interpretation for IBDP Mathematics
Exercise 79
1. The random variable X has the following probability distribution.
x 1 2 3 4
P( X � x)
0.2 0.3 a b
(a)
Find the first equation connecting a and b , giving the answer in the form
pa �qb � r .
It is given that E( X ) � 2.62 .
[2]
(b)
Find the second equation connecting a and b , giving the answer in the form
pa �qb � r .
(c) Hence, write down the values of a and b .
[2]
[2]
2. The random variable X has the following probability distribution.
x 20 30 40 50
P( X � x)
0.1 a b 0.1
It is given that P( X �45) � 0.9 .
(a)
Find the first equation connecting a and b , giving the answer in the form
pa �qb � r .
It is given that E( X ) � 33.
[2]
(b)
Find the second equation connecting a and b , giving the answer in the form
pa �qb � r .
(c) Hence, write down the values of a and b .
[2]
[2]
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