Mathematics 9709 · AS & A Level · Permutations and combinations

Permutations and combinations — practice question

(a)[2]

Determine how many distinct arrangements of the 9 letters in the word ALLIGATOR have the two As adjacent and the two Ls adjacent.

(b)[5]

The 9 letters in the word ALLIGATOR are put in random order. Find the probability that the two Ls are together and there are exactly 6 letters between the two As.

(c)[3]

Find the number of different selections of 5 letters from the 9 letters in ALLIGATOR that contain at least one A and at most one L.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: Permutation formed is $\dfrac{7!}{2!2!}$ or an equivalent expression

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