## randomecorner one year ago What is the surface area of the rectangular prism?

1. randomecorner
2. randomecorner

need help on this one and 2 more

3. anonymous

Hi. The surface area of a right rectangular prism is: A = 2(wl + hl + hw), where A is area, w is width, h is height, and l is length.

4. anonymous

|dw:1433909333961:dw|

5. randomecorner

im cornfusssed

6. randomecorner

im not ''talented'' in math

7. anonymous

It's okay! You're good enough. Practice makes perfect.

8. anonymous

Let's start simply.

9. anonymous

|dw:1433909454486:dw|

10. anonymous

Can you tell me what the area is of that square?

11. randomecorner

area?

12. randomecorner

;-;

13. randomecorner

were u go? @IParke

14. randomecorner

|dw:1433909583762:dw|

15. randomecorner

|dw:1433909621965:dw|

16. anonymous

|dw:1433909631013:dw|

17. randomecorner

oh i thought i got dicthed again lol im judt that bad at math

18. anonymous

How many circles did I draw? Quickly!

19. randomecorner

9

20. anonymous

And how did you know that?

21. randomecorner

3 times 3

22. randomecorner

or there are 3 rows of three circles

23. anonymous

Excellent. Area works the same exact way.

24. anonymous

Now imagine instead of 'circles' I drew 'inches'. Well, to get the total number of inches, it's the same way you calculated the number of circles I drew.

25. anonymous

3 inches x 3 inches = 9 inches

26. anonymous

Are you following?

27. randomecorner

oh so in the problum you times the sides?

28. anonymous

Exactly. So in that square I drew, can you use the letters to tell me what my area should be?

29. anonymous

|dw:1433909867708:dw|

30. randomecorner

4 times h?

31. anonymous

Remember, you found 3x3 because 3 columns and 3 rows. Here I have w columns and h rows. w*h

32. anonymous

Is this clear?

33. randomecorner

kinda [can we use numbers plz]

34. anonymous

Yes, of course.

35. anonymous

|dw:1433909978681:dw|

36. randomecorner

lol thx letters get me confused

37. anonymous

No problem! It's not important here.

38. randomecorner

so 4times 6

39. anonymous

Let's use the values I drew on the square friend ;)

40. randomecorner

wait no you times the 3

41. anonymous

Let me show you why area is stuff like "inches squared" or "centimeters squared"

42. anonymous

43. randomecorner

probably lol

44. anonymous

|dw:1433910092578:dw|

45. anonymous

Quick! How many boxes?

46. randomecorner

24page froze srry

47. anonymous

No problem. And you solved that how?

48. randomecorner

4 times 6

49. anonymous

Exactly :D

50. randomecorner

isnt it lentgh times with

51. anonymous

You are exactly correct.

52. randomecorner

heck to da chaaa

53. anonymous

|dw:1433910316379:dw|

54. anonymous

Now pay close attention to my magic.

55. anonymous

I just changed "boxes" to "inches." Are you following?

56. randomecorner

ya

57. anonymous

This answer here is 24 inches squared because, I have 24 squares that are inches.

58. randomecorner

[after this im goint to draw u a picture]

59. randomecorner

brb cat needs water

60. anonymous

|dw:1433910438339:dw|

61. anonymous

Sure, no problem. Look at the black box I just drew. The box is 1 inch by 1 inch, making it a square. There are 24 of these squares in my 6 inch by 4 inch area.

62. anonymous

This is why it is called 24 inches "squared." I have 24 squares. Are you following?

63. randomecorner

yes

64. randomecorner

|dw:1433910623508:dw|

65. randomecorner

@IParke

66. randomecorner

What is the surface area of the rectangular prism?

67. anonymous

Let's get to that.

68. randomecorner
69. randomecorner

i know i just put it back over here so wedont have to scroll up lol

70. anonymous

|dw:1433910836272:dw|

71. anonymous

This is your rectangular prism, do you agree?

72. randomecorner

ya but its more wider

73. anonymous

Mine isn't drawn to scale, but it will make it easier for me to draw on :)

74. randomecorner

so it throws me off

75. randomecorner

ok i understand

76. anonymous

So, you know what surface area is? It's the area on the outside of this 3d shape.

77. randomecorner

ok so what we do first is leinght timess width?

78. anonymous

|dw:1433911000222:dw|

79. anonymous

Sure. Let's call 12 inches the length and 10 inches the width.

80. anonymous

Do you see the area of this length times width? Can you calculate it?

81. randomecorner

ok sowe get 120

82. anonymous

Excellent, we get 120 inches sq.

83. randomecorner

so we

84. randomecorner

so next we divide by 3?

85. anonymous

|dw:1433911094878:dw|

86. anonymous

No, we do not divide by 3.

87. randomecorner

aww

88. anonymous

Do you see the area I shaded? What is the area of the shaded region?

89. randomecorner

i forgot the word [ive been doing nothing but math since 1;00 am

90. anonymous

|dw:1433911203882:dw|

91. anonymous

The top and bottom of this prism have the same length and width.

92. anonymous

So they both have the same area. Can you see this?

93. anonymous

We have 2 areas that are 12 times 10 = 120 inches squared.

94. randomecorner

ya

95. randomecorner

so we dived them 2?

96. anonymous

We multiple them.

97. randomecorner

why multiply?

98. anonymous

We have 2 areas with 120 inches squared. That equals 120 inches squared + 120 inches squared.

99. randomecorner

so 240

100. anonymous

Remember that the top and bottom both have the same area. There's 2 of these areas on this prism :)

101. anonymous

|dw:1433911367489:dw|

102. randomecorner

103. anonymous

Is this clear?

104. randomecorner

yes it is get ready for take off

105. anonymous

Great.

106. anonymous

|dw:1433911437373:dw|