| Exam Board | OCR |
|---|---|
| Module | S1 (Statistics 1) |
| Year | 2008 |
| Session | January |
| Marks | 7 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Permutations & Arrangements |
| Type | Arrangements with adjacency requirements |
| Difficulty | Easy -1.3 This is a straightforward permutations question testing basic counting principles. Part (i)(a) is simple factorial calculation (5!), part (i)(b) uses standard 'treat as one unit' technique (4! × 2!), and part (ii) is elementary probability with combinations. All are routine textbook exercises requiring only direct application of formulas with no problem-solving insight needed. |
| Spec | 5.01a Permutations and combinations: evaluate probabilities |
1 (i) The letters $\mathrm { A } , \mathrm { B } , \mathrm { C } , \mathrm { D }$ and E are arranged in a straight line.
\begin{enumerate}[label=(\alph*)]
\item How many different arrangements are possible?
\item In how many of these arrangements are the letters A and B next to each other?\\
(ii) From the letters $\mathrm { A } , \mathrm { B } , \mathrm { C } , \mathrm { D }$ and E , two different letters are selected at random. Find the probability that these two letters are A and B .
\end{enumerate}
\hfill \mbox{\textit{OCR S1 2008 Q1 [7]}}