Date | May 2021 | Marks available | 2 | Reference code | 21M.2.AHL.TZ2.7 |
Level | Additional Higher Level | Paper | Paper 2 | Time zone | Time zone 2 |
Command term | Find | Question number | 7 | Adapted from | N/A |
Question
Eight runners compete in a race where there are no tied finishes. Andrea and Jack are two of the eight competitors in this race.
Find the total number of possible ways in which the eight runners can finish if Jack finishes
in the position immediately after Andrea.
in any position after Andrea.
Markscheme
Jack and Andrea finish in that order (as a unit) so we are considering the arrangement of objects (M1)
ways A1
[2 marks]
METHOD 1
the number of ways that Andrea finishes in front of Jack is equal to the number of ways that Jack finishes in front of Andrea (M1)
total number of ways is 8! (A1)
ways A1
METHOD 2
the other six runners can finish in ways (A1)
when Andrea finishes first, Jack can finish in different positions
when Andrea finishes second, Jack can finish in different positions etc
ways (A1)
hence there are ways
ways A1
[3 marks]