Analysis and Approaches for IBDP Maths Ebook 1 | Page 264

Your Practice Set – Analysis and Approaches for IBDP Mathematics
3. Thierry and Jake share a flat. Thierry cooks dinner five nights out of ten. If Thierry does
not cook dinner then Jake does. If Thierry cooks dinner the probability that they have
lasagna is 9
3
. If Jake cooks dinner the probability that they have lasagna is
10 10 .
Let T be the event that Thierry cooks dinner, and L be the event that they have lasagna
in their dinner.
The information above is shown on the following tree diagram.
(a)
Find
(b)
(i) P( T�� L�)
;
(ii) P( L� ) .
Find the probability that
[4]
(i)
Thierry cooks dinner and they do not have lasagna;
(ii) they do not have lasagna, given that Jake cooks dinner.
[5]
The cost for making lasagna for once is 125 dollars. Consider the expenditure on making
lasagna on a particular three days. Let X be the total amount of expenditure.
(c)
(d)
Copy and complete the probability distribution table.
X 0 125 250 375
P( X � x)
54
125
Find the expected expenditure.
[3]
[2]
256
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