7th Grade Math

= Step-by-Step Solutions begin on page R1.

Extra Practice begins on page EP2.

Examples 1–5 Multiply.

14. 8(-12) 15. 11(-20) 16. - 15(4) 17. - 7(10)


15. -7(11) 19. 25(-2) 20. -20(-8) 21. - 16(-5)


16. (-6)^2 23. (-5)^3 24. (-4)^3 25. (-9)^2


17. 
    
    
    
    • 4(-2)(-8) 27. - 3(-2)(1) 28. - 9(-1)(-5) 29. - 4(3)(-2)
    
    
    
    

Write a multiplication expression to represent each situation. Then find

each product and explain its meaning.

Example 6

30. ECOLOGY Wave erosion causes a certain coastline to recede at a rate of
    3 centimeters each year. This occurs uninterrupted for a period of 8 years.

3131 EXERCISE Ethan burns 650 Calories when he runs for 1 hour. Suppose he

runs 5 hours in one week.

Example 7 ALGEBRA Evaluate each expression if w = 4, x = - 8, y = 5, and z = - 3.

32. 
    
    
    
    • 4 w 33. 7 wz 34. - 2 wx 35. wyx
    
    
    
    


33. MULTIPLE REPRESENTATIONS When a movie is rented it has a due date.
    If the movie is not returned on time, a late fee is assessed. Kaitlyn is
    charged $5 each day for a movie that is 4 days late.
    a. WORDS Explain why 4 × (-5) = -20 describes the situation.
    b. ALGEBRA Write an expression to represent the fee when the movie is
    x days late.
    c. WORDS Kaitlyn resolved the problem of the late movie and did not
    have to pay the late fees. Explain why (-4) × (-5) = 20 represents
    this situation. Why is the product a positive integer?

ALGEBRA Evaluate each expression if a = - 6, b = - 4, c = 3, and d = 9.

B 37. - 3 a^2 38. - cd^2   3939 - 2 a + b 40. b^2 - 4 ac

41. GRAPHIC NOVEL Refer to the graphic novel frame below. How many T-shirts
    would Hannah and Dario need to sell to make up the loss in profit?

Refer to the

graphic novel

at the start of

the chapter.

Refe

grap

at th

the c

Lesson 3C Multiply and Divide Integers 107

102_113_C2L3_895130.indd 107 12/29/09 12:50 PM