To find out how many laps Felly swims in 15 minutes, we can use the following approach:

1. First, determine her swimming rate in laps per minute: $\text{Rate} = \frac{35 \text{ laps}}{25 \text{ minutes}} = 1.4 \text{ laps per minute}$

2. Now, multiply this rate by 15 minutes to find out how many laps she swims in that time: $\text{Laps in 15 minutes} = 1.4 \text{ laps per minute} \times 15 \text{ minutes} = 21 \text{ laps}$

Answer: Felly swims 21 laps in 15 minutes.

Would you like details on the approach or have any questions?

Here are 5 additional questions that expand on this problem:

1. If Felly wants to swim for 40 minutes, how many laps would she complete?
2. How long would it take Felly to swim 50 laps at this rate?
3. If Felly increases her speed by 10%, how many laps would she complete in 15 minutes?
4. What would her rate be if she swam 42 laps in 30 minutes?
5. If another swimmer swims at 1.5 laps per minute, how many more laps would they complete than Felly in 15 minutes?

Tip: To solve problems involving rates, always start by finding the unit rate (e.g., laps per minute). This simplifies calculations for any other time interval.