To determine how far Grace ran in 1.5 hours, we first need to find her average pace during the marathon.
Grace ran 26 miles in 4 hours. To find her average speed in miles per hour (mph), we can use the formula:
\[ \text{Average speed} = \frac{\text{Total distance}}{\text{Total time}} = \frac{26 \text{ miles}}{4 \text{ hours}} = 6.5 \text{ mph} \]
Now, to find the distance she ran in 1.5 hours, we can use the formula:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]
Substituting in the values:
\[ \text{Distance} = 6.5 \text{ mph} \times 1.5 \text{ hours} = 9.75 \text{ miles} \]
Therefore, Grace ran 9.75 miles in 1.5 hours.