Mathematics 9709 · AS & A Level · Permutations and combinations

Permutations and combinations — practice question

(a)[3]

Find the number of distinct arrangements of the 9 letters in the word DAFFODILS where a D is placed at each end and the two Fs are not adjacent.

(b)[3]

Find the probability that a randomly selected arrangement of the 9 letters in the word DAFFODILS has exactly 4 letters between the two Ds.

Worked solution & mark scheme

This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “$\frac{7!}{2!}$ shown by itself” …