The speed of the boat is given by the gradient of the line.
Given two points (x1,y1) and (x2,y2) on a graph, the gradient of the line that passes through the two points is given by
[tex]\text{ gradient = }\frac{y_2-y_1}{x_2-x_1}[/tex]
In this case,
the line passes through the points (0,0) and (2,2).
We can set (x1,x2) = (0,0) and (y1,y2) = (2,2)
Therefore,
[tex]\begin{gathered} \text{ gradient = }\frac{2-0}{2-0}=\frac{2}{2}=1 \\ \text{therefore} \\ \text{the speed = 1km/h} \end{gathered}[/tex]
Given that a body travels with speed, s, and in time, t, the distance travelled, d, is given by
[tex]d=st[/tex]
In this case,
s = 1km/h, and t = 15hours
Therefore,
[tex]d=1\times15=15\operatorname{km}[/tex]
Therefore, the boat travelled a distance of 15km
