1. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Chapter 9 Signed Numbers

2. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Subtracting Signed Numbers 9.2

3. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Opposite Numbers The opposite of a positive number is a negative number with the same absolute value. 2– 201345– 1– 3– 4– 5 The opposite of 4 is – 4. 4 + (– 4) = 0 The sum of a number and its opposite is zero. 10 – 4 = 610 + (–4) = 6 15 – 8 = 715 + (–8) = 7 12 – 2 = 1012 + (–2) = 10 Subtracting is the same as adding the opposite.

4. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Subtraction of Signed Numbers To subtract signed numbers, add the opposite of the second number to the first number. Example: Subtract. –6 – 14 –6 + (–14) –20 The opposite of 14 is – 14. Change the subtraction to addition.Perform the addition of the two negative numbers.

5. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Subtraction of Signed Numbers Example: Subtract. –21 – (–13) –21 + (13) –8 The opposite of – 13 is 13. Change the subtraction to addition. Perform the addition. Remember when subtracting two signed numbers: 1.The first number does not change. 2.The subtraction sign is changed to addition. 3.Write the opposite of the second number. 4.Find the result of the addition problem.

6. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Subtraction of Signed Numbers Example: Subtract. Subtraction changed to addition. The LCD is 55. Multiply the fractions. Add the fractions.

7. Copyright © 2012, 2009, 2005, 2002 Pearson Education, Inc. Applied Problems with Signed Numbers Example: Find the difference in altitude between a mountain 5628 feet high and a gorge 350 feet below sea level. 5628 – (–350)= 5628 + 350= 5978 = 5978 feet 5628 feet Sea level 350 feet 5628 feet – (–350 feet ) Difference in altitude