4 The lengths of time in minutes to swim a certain distance by the members of a class of twelve 9 -year-olds and by the members of a class of eight 16 -year-olds are shown below.
| 9-year-olds: | 13.0 | 16.1 | 16.0 | 14.4 | 15.9 | 15.1 | 14.2 | 13.7 | 16.7 | 16.4 | 15.0 | 13.2 |
| 16-year-olds: | 14.8 | 13.0 | 11.4 | 11.7 | 16.5 | 13.7 | 12.8 | 12.9 | | | | |
- Draw a back-to-back stem-and-leaf diagram to represent the information above.
- A new pupil joined the 16 -year-old class and swam the distance. The mean time for the class of nine pupils was now 13.6 minutes. Find the new pupil's time to swim the distance.