Answer:
Explanation:
If the trail is a mile long and is marked every mile with a sign, then there will be one sign at the end of the trail. In addition, there will be signs marking each mile along the trail, including the starting point. Since there are 1 mile markers between the starting point and the end of the trail, there will be a total of:
1 (at the end) + 1 (at the starting point) + 1 (for each mile marker) = 1 + 1 + 1 = 3
Therefore, three signs are needed to mark a mile-long walking trail.