Mathematics 9709 · AS & A Level · Sampling and estimation
Sampling and estimation — practice question
The library has $4$ identical copies of book $A$, $2$ identical copies of book $B$ and $5$ identical copies of book $C$. These $11$ books are placed on a shelf in the library.
(i)[4]
Calculate the number of different arrangements if the books at the two ends are either both book $A$ or both book $B$.
(ii)[5]
Calculate the number of different arrangements if all the books $A$ are adjacent and none of the books $B$ are adjacent.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Work out the arrangements of $AAAAAAAABB$ or $BBBBBBBBBB$ correctly, for example $\frac{9!}{2!25!}$” …