Algebra Demystified 2nd Ed

80 algebra De mystif ieD

DeMYSTiFieD / algebra DeMYSTiFieD / HuttenMuller / 000-0 / Chapter 4

If the temperature decreases 30°, then the temperature drops below 0 °.

–25° –20° –15° –10° –5° 0 ° 5 ° 10 ° 15 ° 20 ° 25 °

This shows that 20 – 10 = 10. Decrease 10°

FIGURE 4-3

–25° –20° –15° –10° –5° 0 ° 5 ° 10 ° 15 ° 20 ° 25 °

This shows that 20 – 30 = –10. Decrease 30°

FIGURE 4-4

In general, subtracting a larger positive number from a smaller positive number

gives us a negative number.

EXAMPLES

Find the difference.

410 – 500 = –90

10 – 72 = –62

CAUtION Be careful what you call these signs; a negative sign in of a number

indicates that the number is smaller than zero. A minus sign between two num-

bers indicates the operation of subtraction. In the equation 3 – 5 = –2, the sign in

front of 5 is a minus sign and the sign in front of 2 is a negative sign. A minus sign

requires two quantities and a negative sign requires one quantity.

PRACTICE

Find the difference.

1. 28 − 30 =


2. 88 − 100 =


3. 25 − 110 =


4. 4 − 75 =


5. 5 − 90 =

EXAMPLES

Find the difference.

PRACTICE

Find the difference.