7th Grade Math

Selected Answers and Solutions R9

Selected Answers and Solutions

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Pages 187–189 Lesson 3-4C

1. 375,400 3. 0.00015
   55 4,510,000 = 4.51 × 1,000,000

The decimal point

moves 6 places.

= 4.51 × 106 The exponent is positive.

7. 9.2 × 10 -^5 9. 3 × 105 11. > 13. 61,000


8. 0.33 17. 0.09014 19. 2,505 21. 0.001


9. 4.99 × 105 25. 6 × 10 -^3 27. 5 × 107


10. 7.8 × 10 -^5 31. 3 × 109 33a. golf 33b. golf


11. < 37. = 39. 3.2 × 10 -^8
    4141 a. The Mount St. Helens eruption is one power of
    ten or 10 times greater than the Ngauruhoe eruption.
    b. Since the powers of ten for both eruptions are the
    same, we can compare the eruptions by comparing 4
    and 2. The Hekla eruption was 2 times greater than
    the Ngauruhoe eruption.


12. 48,396
    45a.
    (4.2 × 105 )(1.5 × 10 -^2 )

(2.5 × (^10) - (^2) ) ; 2.52 × 105 ; 252,000
45b.
(7.8 × 102 )(8.5 × 100 )
(1.6 × 10 - (^1) )(2.5 (^) × 105 ) ; 1.6575 × 10 - (^5) ; 0.000016575

47. Sample answer: The distance between Earth
    and the Sun is 1.55 × 108 km or 155,000,000 km.


48. D 51. 5.21 × 104 ; 52,100 53. 9.2 × 10 -^2 ; 0.092

Pages 190–193 Chapter Study Guide and Review

1. terminating 3. numerators 5. unlike


2. multiply 9. scientifi c notation 11. 107 13. 201


3. < 17. English 19. ^23 21. 1 ^29 23. 1 25. 3 _ 157


4. 2 154 29. 7 12 ^11 h 31. - 2 53 33. 9 ^38 35. 45 cookies


5. 
   
   
   
   • 6 39. 43 41. 31 or 3 times 43. 315 45. 5 -^2
   
   
   
   


6. x-^4 49. 1.96 × 10 -^5

Chapter 4 Equations and

Inequalities

Page 200 Chapter 4 Are You Ready?

1. p + 3 3. j + 10 5. 17 7. 1 9. 29 11. 6 13. 15


2. 50 17. 38 years old
   Pages 202–203 Lesson 4-1A


3. when you are given the fi nal result and asked to
   fi nd an earlier amount 3. Sample answer: In the
   fi rst four games, Hannah scored a total of 83 points.
   In the fourth game, she scored 19 points. In game
   three, she scored 27 points and in the second game,
   she scored 22 points. How many points did she
   score in the fi rst game? To solve, fi rst subtract 19
   from 83, which is 64. Then subtract 27 from 64 to
   get 37. Finally, subtract 22 from 37. So, Hannah
   scored 15 points in her fi rst game.
   55 Work backward. Start with -25 and reverse all
   operations. Subtract -7 to get -18. Add 6 to get

• 
  
  
  
  12. Divide by -3. The original number is 4.
  
  
  13. 19,200 tennis balls 9. Brie is 14 years old.
  
  
  14. 
      
      
      
      13. Raquel’s car gets 1,774,074
          more inches per gallon than an
          aircraft carrier. 15. 1 ten-dollar
          bill, 2 fi ve-dollar bills, and
          7 one-dollar bills
      
      
      
      
  
  
  
  

Pages 211–213 Lesson 4-1D

1. 2 3. - 2


2. d + 120 = 364; 244 ft
   Wilbur’s flight, 364 ft

n 120 ft

Orville’s flight

7. 5 9. 7 11. 7 13. - 3
   1515 r +^6 = -^3
   __-^6 = -^6
   r = - 9


8. 17 19. 7 21. 7 = w + 2; 5h 23. 15 = t - 3;
   18 years old 25. 18.4 27. 6.4 29. -0.68 31. _ 121


9. 187 35. - 121 37. d - 5 = 18; $23


10. 35 + 45 + x = 180; 100°
    4141 -^1 + -^3 + s +^2 =^0
    
    
    • 2 + s = 0
      _____+^2 = +^2
      s = + 2
      43a. s - 65 = 13; 78 mph 43b. d + 52 = 176; 124 ft
      176 f t
    
    
    
    

The Rattler

El Toro

d

52 ft

43c. The solution of each equation is 170; Colossos

is 170 feet tall. 45. The value of y decreases by 2.

47. Sample answer: An offi ce building is 50 stories
    tall. Its height is 25 stories less than an apartment
    building. What is the height of the apartment
    building? 49. I 51. 7

Pages 218–219 Lesson 4-2B

1. 3 3. - 3 5. 81 7. 6 h = 48; 8 h 9. 7 11. - 3


2. 
   
   
   
   • 5
     1515 10 m^ =^7
     10 · 10 m = 10 · 7
     m = 70
   
   
   
   


3. 
   
   
   
   • 36 19. 80 21. 15 w = 300; 20 weeks
     2323 205 = d 3
     3 · 205 = 3 · 3 d
     615 miles = d
   
   
   
   


4. 20.88h = 145; ≈ 6.94 h 27. Sample answer: Raul
   divided by +6 and should have divided by -6;
   x = - 12 29. True; Sample answer: Multiply each

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