To determine the distance between the first and the last sapling when there are seven saplings in a row with a distance of 23 meters between each adjacent pair, follow these steps:
1. Understand the spacing: When there are 7 saplings lined up, there are gaps or intervals between them. The number of these gaps is always one less than the number of saplings.
2. Calculate the number of intervals: With 7 saplings, there are [tex]\(7 - 1 = 6\)[/tex] intervals between them.
3. Determine the distance of each interval: Each of these intervals is 23 meters.
4. Calculate the total distance: Multiply the number of intervals by the distance of each interval to get the total distance between the first and the last sapling.
[tex]\[
\text{Total distance} = \text{Number of intervals} \times \text{Distance between each interval}
\][/tex]
[tex]\[
\text{Total distance} = 6 \times 23 \, \text{meters}
\][/tex]
[tex]\[
\text{Total distance} = 138 \, \text{meters}
\][/tex]
Therefore, the distance between the first and the last sapling is 138 meters.