MHB Change of Position: Word Question

[chuck1]

In a game of tug of war, your team changes -1 and 3/10 (-1.3) feet in position every 10 seconds. What is your change in position after 30 seconds? I said -3.9 but apparently was wrong. What am I missing?
Thanks!

 

[MarkFL]

The only thing I see missing from your response is a unit of measurement, i.e., the change of position would be -3.9 ft. Perhaps they only want the magnitude of the change, as distances are defined to be non-negative lengths.

If we use the relationship between distance, constant speed, and time:

$$d=rt$$

and plug in the given data:

$$r=\frac{1.3\text{ ft}}{10\text{ s}}$$

$$t=30\text{ s}$$

we get:

$$d=\left(\frac{1.3\text{ ft}}{10\text{ s}} \right)\left(30\text{ s} \right)=3.9\text{ ft}$$