Apps. and Interpretation for IBDP Maths Ebook 1 | Page 290

Your Practice Set – Applications and Interpretation for IBDP Mathematics
(b)
Macy plays a game where she tosses two dice.
If the sum is 5, she wins 3 points.
If the sum is less than 5, she wins 2 points.
If the sum is greater than 5, she loses k points.
(i) Write down the probability that the sum is greater than 5.
(ii)
Find the value of k for which Macy’s expected number of points is zero.
[5]
2. In a game, two standard six-sided dice are tossed. Let X be the sum of the scores on the
two dice.
(a)
Find
(i) P( X � 8) ;
(ii) P( X � 8) ;
(b)
(iii) P( X �9 X � 8) .
Rick plays a game where he tosses two dice.
If the sum is 8, he wins 5 points.
If the sum is greater than 8, he wins k points.
If the sum is less than 8, he loses 1 point.
[7]
(i) Write down the probability that the sum is less than 8.
(ii)
Find the value of k for which Rick’s expected number of points is one.
[5]
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