anonymous 4 years ago A sphere of clay is shape into a solid cylindrical figure. If the cylindrical figure is to be 5 cm high with a base radius of 4 cm, find the radius of the initial sphere of clay

1. Mertsj

$V _{c}=\pi r^2h$

2. anonymous

oh

3. anonymous

wait

4. anonymous

What does Vc stand for?

5. Mertsj

$V _{c}=\pi (4)^2(5)=80\pi cm ^{3}$

6. Mertsj

Volume of the cylinder

7. anonymous

so then the answer would be 3.14X462x5?

8. anonymous

i mean 3.14X4^2X5

9. Mertsj

So the sphere must have had the same volume. But the volume of a sphere is: $V=\frac{4}{3}\pi r^3=80\pi$

10. Mertsj

So we need to solve that for the radius of the sphere

11. anonymous

i tried the method, its just that im not sure what the answer is, thank you for helping and all.

12. anonymous

its just 3 problems which i dont get, i did the rest on my own.

13. Mertsj

We are not done yet. Why did you put in the answer?

14. anonymous

15. Mertsj

16. anonymous

i got 3.93, are you sure its right?

17. Mertsj

It's the 3rd root of 60. I got 3.91

18. anonymous

thank you so much, i just have 2 more problems then im finished.

19. Mertsj

Good for you.

20. anonymous

Wait can you tell me if i did this right: Find the volume of a cylinder of height 16 cm and base diameter 40 cm. I got 8038 CM cubed.

21. Mertsj

Hand on. I;m on the phone.

22. anonymous

k

23. Mertsj

V= pi (20)^2(16)=20106.19

24. anonymous

wait so was my answer correct, because i think i did the right way

25. Mertsj

Compare it with mine.

26. anonymous

ok

27. Mertsj

28. anonymous

29. anonymous

i think i might have used it

30. Mertsj

31. anonymous

so this is the answer: 20106.19?

32. Mertsj

The question asked for the radius of the sphere. The radius of the sphere is 3.91 cm

33. anonymous

34. Mertsj

yep

35. Mertsj

Just got off the phone.

36. anonymous

ok so i did this problem by myself, tell me what you think:

37. Mertsj

ok

38. anonymous

Find the volume of an equilateral triangular prism with triangles of side 4 cm and length 10 cm

39. anonymous

i did area x height to get the answer so:

40. Mertsj

So what did you get for the area of the triangle?

41. anonymous

so i got 12 rounded

42. anonymous

i really got 11.994 so i rounded to 12, would that be right?

43. Mertsj

That seems to big.

44. anonymous

oh

45. anonymous

what would the answer be then?

46. Mertsj

Here is the triangle: |dw:1328744624957:dw|

47. anonymous

ya i did that

48. Mertsj

$A=\frac{1}{2}bh$

49. anonymous

so height equals=3.464, then to get area base X height so 3.464X2

50. anonymous

/2

51. Mertsj

$A=\frac{1}{2}(4)(2\sqrt{3})=4\sqrt{3}=6.93$

52. anonymous

oh so the answer is 6.93?

53. Mertsj

That is the area of the base. To get the volume, you have to multiply that by the height.

54. anonymous

ok

55. anonymous

so the answer is approximately 24?

56. Mertsj

10(6.93)=69.3

57. anonymous

i was wrong?

58. Mertsj

|dw:1328744898001:dw|

59. Mertsj

See that picture? You have to take the area of the triangle and multiply it by the height of the prism which is 10

60. anonymous

but i did 6.93x the height, which is 3.464, and i got 24, is that right?

61. Mertsj

Do you see that picture?????? The HEIGHT OF THE PRISM IS 10.

62. Mertsj

Multiply the AREA OF THE TRIANGLE BY THE HEIGHT OF THE PRISM

63. anonymous

ok thx

64. Mertsj

The height of the prism is 10

65. Mertsj

yw

66. anonymous

|dw:1328745230091:dw|

67. anonymous

68. Mertsj

69. anonymous

all of the inside

70. Mertsj

|dw:1328745481111:dw|

71. Mertsj

Add the two areas together. 120+24 = 144

72. anonymous

Ok, great, thats what i got

73. anonymous

|dw:1328745544210:dw|

74. anonymous

find the area

75. Mertsj

|dw:1328745737456:dw|

76. Mertsj

Is that a 39 or not?

77. anonymous

39 and 34 are to big dont you think?

78. Mertsj

Yes. What is that number you wrote on the left side of the drawing?

79. anonymous

oh thats 9

80. Mertsj

|dw:1328745967893:dw|

81. Mertsj

Is that it?

82. anonymous

ya i think 7 and 4 are more reasponsible, considering thats what i got as well. Then i did 7X4+2X5, getting 38 m

83. anonymous

Is that correct?

84. anonymous

hello?

85. Mertsj

That's what I got.