Fundamentals of Mathematics, 2008a

604 CHAPTER 10. SIGNED NUMBERS
10.6.5.1 Exercises for Review
Exercise 10.6.44 (Solution on p. 626.)
(Section 6.3) Convert 16.02 1 5
to a decimal.
Exercise 10.6.45
(Section 6.6) Find 4.01 of 6.2.
Exercise 10.6.46 (Solution on p. 626.)
(Section 7.5) Convert 5
16
to a percent.
Exercise 10.6.47
(Section 8.4) Use the distributive property to compute the product: 15 · 82.
Exercise 10.6.48 (Solution on p. 626.)
(Section 10.5) Find the sum: 16 + (−21).
10.7 Multiplication and Division of Signed Numbers 7
10.7.1 Section Overview
• Multiplication of Signed Numbers
• Division of Signed Numbers
• Calculators
10.7.2 Multiplication of Signed Numbers
Let us consider rst, the product of two positive numbers. Multiply: 3 · 5.
3 · 5 means 5 + 5 + 5 = 15
This suggests 8 that
(positive number) · (positive number) = (positive number)
More briey,
(+) (+) = (+)
Now consider the product of a positive number and a negative number. Multiply: (3) (−5).
(3) (−5) means (−5) + (−5) + (−5) = −15
This suggests that
(positive number) · (negative number) = (negative number)
More briey,
(+) (−) = (−)
By the commutative property of multiplication, we get
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8 In later mathematics courses, the word "suggests" turns into the word "proof." One example does not prove a claim.
Mathematical proofs are constructed to validate a claim for all possible cases.
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