Let's break down this problem step by step to determine the expression representing Nikita's distance for the second part of the race.

Information given:

• Nikita ran a 5-kilometer race in 39 minutes (which is 0.65 hours).
• Part 1:
  • Speed: 8.75 km/h
  • Time: t hours
  • Distance = Rate × Time = $8.75 \times t$ kilometers
• Part 2:
  • Speed: 6 km/h
  • Time: $0.65 - t$ hours (since the total time is 0.65 hours, the time for Part 2 is the remaining time)
  • Distance = Rate × Time = $6 \times (0.65 - t)$

The total distance covered is 5 kilometers: $\text{Distance for Part 1} + \text{Distance for Part 2} = 5 \, \text{km}$ So: $8.75t + 6(0.65 - t) = 5$

From this, the expression representing the distance for the second part of the race is: $6(0.65 - t)$

Therefore, the correct answer is the option: $\boxed{6(0.65 - t)}$

Would you like a detailed explanation of the next steps in solving this equation, or do you have any other questions?

Related Questions:

1. How would you solve the equation to find the value of $t$?
2. What would the distance for Part 1 of the race be?
3. How much time did Nikita spend in the second part of the race?
4. What percentage of the total time did Nikita spend running at 6 km/h?
5. How would the expression change if the total time was different?

Tip: Always remember that time, rate, and distance are interconnected by the formula $\text{Distance} = \text{Rate} \times \text{Time}$.