Find the number of different ways that 5 boys and 6 girls can stand in a row if all the boys stand together and all the girls stand together.
- (i)Find the number of different ways that 5 boys and 6 girls can stand in a row if all the boys stand together and all the girls stand together.[3]
- (ii)Find the number of different ways that 5 boys and 6 girls can stand in a row if no boy stands next to another boy.[3]
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2018). The mark or mark type is shown in brackets.
- [B1] k×5! or m×6! (k,m integer, k,m ≥ 1), no inappropriate addition
- [B1] n × 5! × 6! (n integer, n ≥ 1), no inappropriate addition
- [B1] Correct final answer, isw rounding (www scores B3) All marks based on their final answer
- [M1] k× 6! or k × ⁷P₅ (k is an integer, k ≥ 1) no inappropriate add. (⁷P₅ = 7 × 6 × 5 × 4 × 3 or ⁷C₅ × 5!)
- [M1] Correct unsimplified expression
- [A1] Correct exact final answer (ignore subsequent rounding)
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