D1 January 2007 Q2
2.


Figure 1 shows the possible allocations of five people, Ellen, George, Jo, Lydia and Yi Wen to five tasks, 1, 2, 3, 4 and 5.
Figure 2 shows an initial matching.
(a) Find an alternating path linking George with 5. List the resulting improved matching this gives. (3)
(b) Explain why it is not possible to find a complete matching. (1)
George now has task 2 added to his possible allocation.
(c) Using the improved matching found in part (a) as the new initial matching, find an alternating path linking Yi Wen with task 1 to find a complete matching. List the complete matching. (3)
| Scheme | Marks |
|---|---|
| \(G - 3 = J - 4 = L - 5\) | M1 |
| change status: \(\underline{G = 3 - J = 4 - L = 5}\) | A1 |
| Improved matching: \(E = 2,\ G = 3,\ J = 4,\ L = 5\) | B1 |
| (3) |
| Scheme | Marks |
|---|---|
| e.g. George and Yi Wen may both only be assigned to 3 | B1 |
| (1) |
| Scheme | Marks |
|---|---|
| \(Y - 3 = G - 2 = E - 4 = J - 1\) | M1 |
| change status: \(\underline{Y = 3 - G = 2 - E = 4 - J = 1}\) | A1 |
| complete matching: \(E = 4,\ G = 2,\ J = 1,\ L = 5,\ Y = 3\) | A1 |
| (3) | |
| (7 marks) |