How many different arrangements are there of the 10 letters in the word REGENERATE?
- (a)How many different arrangements are there of the 10 letters in the word REGENERATE?[1]
- (b)How many different arrangements are there of the 10 letters in the word REGENERATE in which the 4 Es are together and the 2 Rs have exactly 3 letters in between them?[4]
- (c)Find the probability that a randomly chosen arrangement of the 10 letters in the word REGENERATE is one in which the consonants (G, N, R, R, T) and vowels (A, E, E, E, E) alternate, so that no two consonants are next to each other and no two vowels are next to each other.[5]
Mark scheme
Marking points from the official mark scheme (May/June 2024). The mark or mark type is shown in brackets.
- [B1] [10! / (2!4!)] = 75600
- [M1] 4! SOI in all terms leading to final answer. Allow 24 if 4! = 24 is seen.
- [M1] Ignoring any values used to justify 4!. Either 3! SOI in expression leading to final answer, or at least 6 distinct scenarios identified and added in expression leading to final answer. Condone 3 distinct scenarios × 2. Ignore repeated scenarios.
- [A1] 4! × 3! Fully correct unsimplified expression leading to final answer.
- [B1] WWW
- [B1] 5!/2! seen (arrangements of consonants).
- [B1] 5!/4! seen (arrangements of vowels).
- [M1] 5!/r! × 5!/s! × 2, r = 1 or 2, s = 1, 4, 4! or 24.
- [M1] their 600 / their (a) or their 600 / 75600
- [A1] Accept 600/75600 OE.
- [(B1)] 5! seen (arrangements of consonants).
- [(B1)] A second 5! seen (arrangements of vowels).
- [(M1)] 5! × 5! × k, k = 1 or 2.
- [(M1)] their 28800 / 10!
- [(A1)] Accept 600/75600 OE.
- [(B1)] 5/10 × 4/9 × 3/8 × 2/7 × 1/6 seen.
- [(B1)] A second 5/10 × 4/9 × 3/8 × 2/7 × 1/6 seen.
- [(M1)] 5/10 × 4/9 × ... × k.
- [(M1)] their 5×4×3×2×1×5×4×3×2×1 / 10×9×8×7×6×5×4×3×2×1
- [(A1)] Accept 28800/362800 OE.
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