Algebra Demystified 2nd Ed

Chapter 4 NegaTive NuMberS 81

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

SOLUTIONS

1. 28 − 30 = −2


2. 88 − 100 = −12


3. 25 − 110 = −85


4. 4 − 75 = −71


5. 5 − 90 = −85

Subtracting a Positive Number from a Negative Number

Let us see the effect of subtracting a positive number from a negative num-

ber. Returning to the temperature example, suppose the temperature is –10°

and the temperature drops another 5°, then the temperature is even further

below 0°.

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

Decrease 5° This shows that –10 – 5 = –15.

FIGURE 4-5

When subtracting a positive number from a negative number, add the num-

bers (ignoring the negative sign). The difference is negative.

EXAMPLES

Find the difference.

–30 – 15 = –45

–18 – 7 = –25

–500 – 81 = –581

PRACTICE

Find the difference.

1. −16 − 4 =


2. −70 − 19 =


3. −35 − 5 =


4. −100 − 8 =


5. −99 − 1 =

EXAMPLES

Find the difference.

PRACTICE

Find the difference.

SOLUTIONS

1. 28 −