Analysis and Approaches for IBDP Maths Ebook 1 | Page 282

Your Practice Set – Analysis and Approaches for IBDP Mathematics
Exercise 91
1. The random variable X is normally distributed with a mean of 80. The following
diagram shows the normal curve for X .
Let R be the shaded region under the curve, to the right of 86. The area of R is 0.28.
(a) Write down P( X � 86) .
(b) Find P(80 � X � 86) .
(c) Find P(74 � X � 80) .
[1]
[3]
[2]
2. The random variable X is normally distributed with a mean of 300. The following
diagram shows the normal curve for X .
Let R be the shaded region under the curve, to the left of 270. The area of R is 0.15.
(a) Write down P( X � 270) .
(b) Find P(270 � X � 300) .
(c) Find P(270 � X � 330) .
[1]
[3]
[2]
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