To solve the problem, let's calculate the cost per hour to run the fan and then determine the cost for 6 hours.

Step 1: Determine the cost per hour.

We are told that it costs $0.60 to run the fan for 4 hours: $\text{Cost per hour} = \frac{\text{Total cost}}{\text{Number of hours}} = \frac{0.60}{4} = 0.15 \, \text{(dollars per hour)}.$

Step 2: Calculate the cost for 6 hours.

The cost for 6 hours can be calculated by multiplying the cost per hour by the number of hours: $\text{Cost for 6 hours} = \text{Cost per hour} \times \text{Number of hours} = 0.15 \times 6 = 0.90 \, \text{dollars}.$

Final Answer:

The cost to run the fan for 6 hours is $0.90 (Option D).

Would you like a detailed explanation or have any questions?
Here are 5 related questions to expand your understanding:

1. How would the calculation change if the cost for 4 hours was $1.20 instead of $0.60?
2. How do we generalize this to calculate the cost for any number of hours?
3. What if electricity rates vary depending on the time of day?
4. How can you double-check such calculations for accuracy?
5. How would the result change if the hours were reduced to 2?

Tip:

When solving proportional problems, always check the unit rates first to simplify calculations.