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Date May 2013 Marks available 3 Reference code 13M.1.sl.TZ1.5
Level SL only Paper 1 Time zone TZ1
Command term Find Question number 5 Adapted from N/A

Question

The probability that Tanay eats lunch in the school cafeteria is \(\frac{3}{5}\).

If he eats lunch in the school cafeteria, the probability that he has a sandwich is \(\frac{3}{{10}}\).

If he does not eat lunch in the school cafeteria the probability that he has a sandwich is \(\frac{9}{{10}}\).

Complete the tree diagram below.

[3]
a.

Find the probability that Tanay has a sandwich for his lunch.

[3]
b.

Markscheme

     (A1)(A1)(A1)     (C3)


Note: Award (A1) for each correct pair of branches.

a.

\(\frac{3}{5} \times \frac{3}{{10}} + \frac{2}{5} \times \frac{9}{{10}}\)     (A1)(ft)(M1)


Notes: Award (A1)(ft) for their two correct products, (M1) for addition of their products. Follow through from their tree diagram.


\( = \frac{{27}}{{50}}(0.54,54\% )\)     (A1)(ft)     (C3)

b.

Examiners report

[N/A]
a.
[N/A]
b.

Syllabus sections

Topic 3 - Logic, sets and probability » 3.7 » Probability of combined events, mutually exclusive events, independent events.
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