Working with Negative Numbers

Suppose each time a football team started on offense

they were at MID-FIELD. (Also assume that the

field is marked like a number line!)

Determine the position of the ball

after these sequences of plays:

Gain 10, Lose 5

The ball would rest on the 5 YARD LINE.

In math this would be represented by the

ADDITION PROBLEM:

(10) + (-5)  = 5

Thus, it seems that we are subtracting 10 minus 5.

And since the Gain is LARGER the ball is in the

POSITIVE DIRECTION

Try this set of plays starting at MID-FIELD:

Lose 30, Gain 20

ADDITION PROBLEM:

(-30) + (20) = -10
Again we subtract the numbers and the answer
has the sign of the LARGER  "-" (in size)

RULE:
When adding TWO numbers with
OPPOSITE SIGNS, subtract and
use the SIGN of the "LARGER"
(IN SIZE)

A review of PEMDAS might be in order before
attempting the following problems:

   

Simplify Arithmetic Expressions

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