| Date | May 2011 | Marks available | 3 | Reference code | 11M.1.sl.TZ1.4 |
| Level | SL only | Paper | 1 | Time zone | TZ1 |
| Command term | Write down | Question number | 4 | Adapted from | N/A |
Question
Police in a town are investigating the theft of mobile phones one evening from three cafés, “Alan’s Diner”, “Sarah’s Snackbar” and “Pete’s Eats”.
They interviewed two suspects, Matthew and Anna, about that evening.
Matthew said:
“I visited Pete’s Eats and visited Alan’s Diner and I did not visit Sarah’s Snackbar.”
Let \(p\) , \(q\) and \(r\) be the statements:
\(p\) : I visited Alan’s Diner
\(q\) : I visited Sarah’s Snackbar
\(r\) : I visited Pete’s Eats
Write down Matthew’s statement in symbolic logic form.
What Anna said was lost by the police, but in symbolic form it was
\[(q \vee r) \Rightarrow \neg p\]
Write down, in words, what Anna said.
Markscheme
\(r \wedge p \wedge \neg q\) (A1)(A1)(A1) (C3)
Note: Award (A1) for two conjunctions, (A1) for negation seen on \(q\), (A1) for correct compound statement.
[3 marks]
If I visited (either) Sarah’s Snackbar or Pete’s Eats (then) I did not visit Alan’s Diner. (A1)(A1)(A1) (C3)
Note: Award (A1) for If\( \ldots \) (then), (A1) for Sarah’s Snackbar or Pete’s Eats, (A1) for did not visit Alan’s Diner.
[3 marks]
Examiners report
The logic question was clearly difficult for many students. Part a was very poorly done with the majority of students not recognising that two conjunctions were required. Although candidates performed better on part b, many omitted the 'if, (then)'. One of the most common errors in part b was to translate the disjunction as 'and' rather than 'or'.
The logic question was clearly difficult for many students. Part a was very poorly done with the majority of students not recognising that two conjunctions were required. Although candidates performed better on part b, many omitted the 'if, (then)'. One of the most common errors in part b was to translate the disjunction as 'and' rather than 'or'.
