Analysis and Approaches for IBDP Maths Ebook 1 | Page 288

Your Practice Set – Analysis and Approaches for IBDP Mathematics
Exercise 93
1. In a village, the time taken for students to travel to school is normally distributed with
mean � and standard deviation � . It is found that 39% of the students take less than 10
minutes to get to school, and 11% take more than 13 minutes. Find the value of � and of
� .
[8]
2. A random variable X is normally distributed with � and � . It is given that 42% of the
data are greater than 58, and 1% of the data are greater than 69. Find the value of � and
of � .
[8]
3. A random variable X is normally distributed with � and � . It is given that 20% of the
data are greater than 20 and less than � , and 30% of the data are greater than � and less
than 24. Find the value of � and of � .
[8]
4. A random variable X is normally distributed with � and � . It is given that 10% of the
data are greater than 180 and less than � , and 9% of the data are greater than 192 and
less than �� � . Find the value of � and of � .
[8]
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