Question

Question: A football team lost 9 yards on its first play. It then gained 9 yards on its second play. A. What expression can be written to represent how many yards the football team is from where it started? Explain your reasoning. B. How many yards is the football team from where it started? C. Suppose that, instead, the football team had gained 9 yards on its first play and lost 9 yards on its second play. Would the team’s position on the field have been any different than it actually was after the first two plays? Why or why not?

Answer 1

You can consider lost yards as negative, and gaines yards as positive. So, if they lost 9 yards and then gained 9 yards, the expression is

$-9+9 = 0$

This means that the team is exactly where it started (which maked sense, because they lost exactly as much as they gained.

If they gained first and lost then, it wouldn't change a thing: you'd have

$9-9=0$

and so the team is always where it started.