If the ends span from the 0 to the 15 meter mark, then the length of the pipe is 15 meters. However, you should report it using the right amount of significant figures. It is mentioned in the problem that millimeter marks are calibrated between meters. Since millimeter is 1/1000 of a meter, you should add three decimal places to the 15 meters. Hence, you should report it as 15.000 meters.
You could use a 25 pound bag of rolled oats 7 times
Answer: The point (0,0)
This point is also known as the origin
The reason why is because every direct variation equation is of the form y = k*x
where k is some fixed number
If we plugged in x = 0 it leads to y = k*x = k*0 = 0. So (x,y) = (0,0)