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Module 2-3

Pages (102-108)

EQ: How is mathematics helpful in search and rescue operations?

Signed numbers let us show directions. It often helps us indicate above or below a certain reference point. For example, below zero degrees on a thermometer is indicated by a negative number and below sea level is also indicated by a negative number.

Adding Signed Numbers

If the signs are the same:
    Step 1:   Add the numbers.
    Step 2:   The answer will have the original sign.
          +3 + +7 = +10
          -3 + -7 = -10
If the signs are different:
   Step 1:    Subtract the smaller absolute value from the larger absolute value.
   Step 2:    The answer will have the sign of the larger number.
          +3 + -7 = -4 (7-3=4)      the sign of the larger value is negative so the answer is -4
          -3 + +7 = +4 (7-3=4)       the sign of the larger value is positive so the answer is+4
It does not matter which number is listed first!

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