Apps. and Interpretation for IBDP Maths Ebook 1 | Page 281

3. The random variable X has the following probability distribution.
x 0 10 20 30
P( X � x)
0.1 a b c
It is given that P( X �15) � 0.5.
(a) Find the value of a .
It is also given that E( X ) � 16 .
[2]
(b) Find the values of b and c .
The observation of X is recorded for two times. Let Y be the sum of these two
observations.
[4]
(c) Find P( Y � 50) .
[2]
4. The random variable X has the following probability distribution.
19
x 0 3 6 9
P( X � x)
0.4 a b c
It is given that P(2 � X �7) � 0.3.
(a) Find the value of c .
It is also given that E( X ) � 4.2 .
[2]
(b) Find the values of a and b .
The observation of X is recorded for two times. Let Y be the product of these two
observations.
[4]
(c) Find P( Y � 36) .
[2]
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