The problem states:

• The trail is 2.5 kilometers long.
• Ashley has already walked 0.72 kilometers.
• We need to determine how many more kilometers she needs to walk to complete the trail.

Solution:

To find the remaining distance, subtract the distance Ashley has already walked from the total length of the trail:

$\text{Remaining distance} = \text{Total distance} - \text{Distance walked}$

$\text{Remaining distance} = 2.5 - 0.72 = 1.78 \, \text{kilometers}$

Final Answer:

The correct choice is: C. 1.78

Would you like more details or have any questions?

Related Questions:

1. How do we ensure subtraction with decimals is accurate?
2. What is a real-world example where subtraction of distances might be useful?
3. How do you check if the answer is reasonable?
4. What if Ashley had walked 1.5 kilometers instead of 0.72?
5. How could this problem be represented on a number line?

Tip:

When subtracting decimals, always align the decimal points to avoid errors.