To convert kilometers to miles, Judy can use the conversion factor that 1 kilometer is approximately 0.6 miles. To find the equivalent distance in miles for 40 kilometers, she can perform the following calculation:
\[ \text{Distance in miles} = \text{Distance in kilometers} \times \text{Conversion factor} \]
Substituting the values:
\[ \text{Distance in miles} = 40 , \text{kilometers} \times 0.6 , \text{miles/kilometer} \]
Calculating this gives:
\[ \text{Distance in miles} = 40 \times 0.6 = 24 , \text{miles} \]
Thus, Judy's estimate for the 40 kilometers is approximately 24 miles.