The number line is an essential idea in pre algebra, it can be used to solve simple equations or to represent types of numbers such as natural numbers or whole numbers. In addition, American Football is is one of the few sports that has a good representation of the number line.

Example: On their second down, the Patriots are on their 21 yard line. On the third down they're on their 38 yard line. In order to find out how far they moved the ball on the second down, we can draw a number line and use the variables:

s = their field position on the second down

t = their field position on the third down

m = the number of yards moved on the second down

Since we know s = 21 and t = 38 we can use these variables and the number line to find out m.

By looking at the number line above, we know that:

t = s + m

38 = 21 + m (subtract 21 on each side)

38 (-21) = 21 + (-21) + m

m = 17

Answer: The Patriots moved 17yards on the second down.

Heres the Football field: