The 9 letters in the word HAPPINESS are divided at random into a group of 5 and a group of 4.
- (a)Find the number of different arrangements of the 9 letters in the word HAPPINESS.[1]
- (b)Find the number of different arrangements of the 9 letters in the word HAPPINESS in which the first and last letters are not the same as each other.[3]
- (c)Find the number of different arrangements of the 9 letters in the word HAPPINESS in which the two Ps are together and there are exactly two letters between the two Ss.[4]
- (d)The 9 letters in the word HAPPINESS are divided at random into a group of 5 and a group of 4. Find the probability that both Ps are in one group and both Ss are in the other group.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.
- [B1]
- [M1] a – 7!/2! × b a= their 6(a) or correct, b = 1,2.
- [M1] a – 7!/c! × 2 a = their 6(a) or correct, c = 1,2.
- [A1 FT] ft their 6(a) – 5040.
- [M1] Finding correct number of ways for one of these correctly identified scenarios.
- [M1] Adding no of ways for 3 correctly identified scenarios.
- [A1]
- [M1] Finding correct number of ways for one of these correctly identified scenarios.
- [M1] Adding no of ways for 3 correctly identified scenarios.
- [A1]
- [M1] Identifying no of ways if S^^S is in position 1 or 6.
- [M1] Identifying no of ways if S^^S is in position 2, 3, 4 or 5.
- [M1] Adding no of ways for 6 scenarios (or 26 × 5!).
- [A1] SC B1 for 3120 if any method marks are withheld.
- [M1] a×⁵C₂, a×⁵C₃, or ⁵C₂+⁵C₃ seen as a numerator of one or two fractions where a is 1 or 2, no extra terms.
- [M1] ⁹C₅ or ⁹C₄ seen (no addition, multiplication) as a denominator of one or two fractions.
- [A1]
- [M1] a×5×4×4×3 seen as a numerator of a fraction. where a = 1 or 2.
- [M1] 9×8×7×6 seen as a denominator of a fraction.
- [A1]
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