Apps. and Interpretation for IBDP Maths Ebook 1 | Page 298

Your Practice Set – Applications and Interpretation for IBDP Mathematics
Exercise 84
1. A factory makes switches. The probability that a switch is defective is p . The factory
tests a random sample of 120 switches.
(a)
(b)
Write down an expression, in terms of p , for the probability that there are exactly
three defective switches in the sample.
[2]
Hence, find the possible values of p such that the probability that there are
exactly three defective switches in the sample is 0.16.
[3]
2. Sandy goes to work five days a week. On any day, the probability that she goes on a bus
is p .
(a)
(b)
Write down an expression, in terms of p , for the probability that she goes to
work on a red bus on exactly four days.
Hence, find the possible values of p such that the probability that she goes to
work on a red bus on exactly four days is 0.3.
[2]
[3]
3. The probability of obtaining “tails” when a biased coin is tossed is q . The coin is tossed
ten times.
(a)
(b)
Write down an expression, in terms of q , for the probability of obtaining at least
nine tails.
[2]
Hence, find the value of q such that the probability of obtaining at least nine tails
is 0.09.
[3]
4. There are one hundred customers in a café in a particular day. The probability that a
customer buys chocolate muffins is q .
(a)
(b)
Write down an expression, in terms of q , for the probability that there are at most
one customer buying chocolate muffins.
[2]
Hence, find the value of q such that the probability that there are at most one
customer buying chocolate muffins is 0.03.
[3]
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