To find out how far Nathan can walk in 1.75 hours at a speed of 2.5 miles per hour, you can use the formula:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]
Substituting the values:
\[ \text{Distance} = 2.5 , \text{miles/hour} \times 1.75 , \text{hours} \]
Calculating this:
\[ \text{Distance} = 2.5 \times 1.75 = 4.375 , \text{miles} \]
Therefore, Nathan can walk 4.375 miles in 1.75 hours.