Answer :

To solve for the average speed of Tatjana Schoenmaker in swimming across the pool and then returning to the starting point, let's break down the problem step-by-step:

1. Determine the time for one length of the pool:
- Tatjana takes 23.2 seconds to swim one length of the pool.

2. Determine the extra time to return:
- Returning to the starting point takes her 1.7 seconds more than the time taken for one length.
- To find the return time:
[tex]\[ \text{Return time} = 23.2 \; \text{seconds} + 1.7 \; \text{seconds} = 24.9 \; \text{seconds} \][/tex]

3. Calculate the total time to complete the event:
- Total time includes the time for one length plus the return time.
[tex]\[ \text{Total time} = 23.2 \; \text{seconds} + 24.9 \; \text{seconds} = 48.1 \; \text{seconds} \][/tex]

4. Calculate the total distance swum:
- Tatjana swims two lengths of the pool (one length to the end and one length back to the starting point).
[tex]\[ \text{Total distance} = 2 \; \text{lengths} \][/tex]

5. Calculate the average speed:
- Speed is given by the formula:
[tex]\[ \text{Average speed} = \frac{\text{Total distance}}{\text{Total time}} \][/tex]
- Here, the total distance is 2 lengths of the pool, and the total time is 48.1 seconds. So, the average speed is:
[tex]\[ \text{Average speed} = \frac{2 \; \text{lengths}}{48.1 \; \text{seconds}} \approx 0.04158 \; \text{lengths per second} \][/tex]

Therefore, Tatjana's average speed to complete the event is approximately [tex]\( 0.04158 \)[/tex] lengths per second.