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Date May 2011 Marks available 2 Reference code 11M.1.sl.TZ2.9
Level SL only Paper 1 Time zone TZ2
Command term Find Question number 9 Adapted from N/A

Question

A survey was carried out at an international airport. A number of travellers were interviewed and asked for their flight destinations. The results are shown in the table below.

One traveller is to be chosen at random from all those interviewed.

Find the probability that this traveller was going to Africa.

[2]
a.

One female traveller is to be chosen at random from all those interviewed.

Find the probability that this female traveller was going to Asia.

[2]
b.

One traveller is to be chosen at random from those not going to America.

Find the probability that the chosen traveller is female.

[2]
c.

Markscheme

\(\frac{{108}}{{250}}{\text{ }}\left( {\frac{{54}}{{125}}{\text{, }}0.432{\text{, }}43.2\% } \right)\)     (A1)(A1)     (C2)

Note: Award (A1) for numerator, (A1) for denominator.

[2 marks]

a.

\(\frac{{25}}{{106}}{\text{ }}\left( {0.236{\text{, }}23.6\% } \right)\)     (A1)(A1)     (C2)

Note: Award (A1) for numerator, (A1) for denominator.

[2 marks]

b.

\(\frac{{71}}{{170}}{\text{ }}\left( {0.418{\text{, }}41.8\% } \right)\)     (A1)(A1)     (C2)

Note: Award (A1) for numerator, (A1) for denominator.

[2 marks]

c.

Examiners report

A reasonably well attempted question with parts (a) and (c) proving to provide many correct answers. A correct answer for part (b) however proved to be a little more elusive as, despite a correct numerator of \(25\) seen on many scripts, the total sample space was not reduced and a denominator of \(250\) lost the final mark in this part of the question. On a minority of scripts candidates simply wrote down decimal answers. Where these were correct, both marks for each part were earned. However, incorrect answers earned no marks – candidates would be well advised to at least write down the fraction answer first so that any part marks can be awarded. A case in question here was a predominance of incorrect answers of \(0.10\) or \(10\% \) for part (b). This, on its own earns no marks whereas \(25/250\) earned A1, A0.

a.

A reasonably well attempted question with parts (a) and (c) proving to provide many correct answers. A correct answer for part (b) however proved to be a little more elusive as, despite a correct numerator of \(25\) seen on many scripts, the total sample space was not reduced and a denominator of \(250\) lost the final mark in this part of the question. On a minority of scripts candidates simply wrote down decimal answers. Where these were correct, both marks for each part were earned. However, incorrect answers earned no marks – candidates would be well advised to at least write down the fraction answer first so that any part marks can be awarded. A case in question here was a predominance of incorrect answers of \(0.10\) or \(10\% \) for part (b). This, on its own earns no marks whereas \(25/250\) earned A1, A0.

b.

A reasonably well attempted question with parts (a) and (c) proving to provide many correct answers. A correct answer for part (b) however proved to be a little more elusive as, despite a correct numerator of \(25\) seen on many scripts, the total sample space was not reduced and a denominator of \(250\) lost the final mark in this part of the question. On a minority of scripts candidates simply wrote down decimal answers. Where these were correct, both marks for each part were earned. However, incorrect answers earned no marks – candidates would be well advised to at least write down the fraction answer first so that any part marks can be awarded. A case in question here was a predominance of incorrect answers of \(0.10\) or \(10\% \) for part (b). This, on its own earns no marks whereas \(25/250\) earned A1, A0.

c.

Syllabus sections

Topic 3 - Logic, sets and probability » 3.7 » Use of tree diagrams, Venn diagrams, sample space diagrams and tables of outcomes.
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