## anonymous one year ago help plz

1. anonymous

The coordinates A(0, 0), B(0, 5) and C(3, 0) are graphed and connected together. What 3-dimensional shape will be created when this shape is rotated about the y-axis? Provide an explanation and proof for your answer to receive full credit.

2. anonymous

@yoongi

3. anonymous

help plz

4. nerdyotter

A great tool for graphing this would be Desmos, if you haven't already used it. It should be able to help you visualize what the pre-image of the shape (before rotation) will look like. https://www.desmos.com/calculator

5. anonymous

can u still help me

6. nerdyotter

It looks like the shape's pre-image will be a triangle with the right angle at the origin. What would happen if you rotated this shape 360 degrees?

7. nerdyotter

8. anonymous

i will be a cone

9. anonymous

it

10. nerdyotter

Correct!

11. anonymous

thanks

12. nerdyotter

No problem!

13. anonymous

i have 2 more question if you dont mind

14. nerdyotter

I'll answer them the best I can.

15. anonymous

Which of these countries has the greatest population density? Which has the least? Provide an explanation and proof for your answer to receive full credit.

16. anonymous

Country Population (1997 estimate) Area (square km) U.S. 272,648,000 9,364,520 Romania 22,609,000 237,391 Ghana 18,339,000 237,533

17. nerdyotter

I guess I'm just not really sure what that question is trying to ask.

18. anonymous

Country Population Area square km) U.S. 272,648,000 9,364,520 Romania 22,609,000 237,391 Ghana 18,339,000 237,533

19. anonymous

is that a better chart

20. anonymous

Which of these countries has the greatest population density? Which has the least? Provide an explanation and proof for your answer to receive full credit

21. nerdyotter

I'm assuming it's asking you to find the number of people per square kilometer. I'm not ENTIRELY sure what to do here, but I'm assuming you could simply divide the population by the number of square kilometers (the area) to get that information.

22. anonymous

okk

23. nerdyotter

For example, the US would be 272,648,000 / 9,364,520 = 29.115.

24. anonymous

ok

25. anonymous

the last question

26. anonymous

Pyramid A is a square pyramid with a base side length of 14 inches and a height of 6 inches. Pyramid B has a volume of 3,136 cubic inches. How many times bigger is the volume of pyramid B than pyramid A? Give your answer as a percent. Provide an explanation and proof for your answer to receive full credit.

27. nerdyotter

Do you know how to calculate the volume of a square pyramid?

28. anonymous

V=bh1/3 i believe

29. nerdyotter

The formula is $\frac{ 1 }{ 3 } b ^{2} h$ or $b ^{2} \frac{ h }{ 3 }$ Knowing this, what would you get for the volume of the first square pyramid?

30. anonymous

14^3 6/3

31. anonymous

v=1372

32. nerdyotter

That's b squared, not b cubed.

33. anonymous

ok hold up let me add it again

34. anonymous

v=98

35. nerdyotter

I think you're getting caught up somewhere in the calculation. Let's take this step by step.

36. anonymous

14*14=196 6/3=2 196/2=98

37. nerdyotter

$b ^{2} \frac{ h }{ 3 }$ $14^{2} \frac{ 6 }{ 3 }$ $196(\frac{ 6 }{ 3 }) = ? ^{3}$

38. nerdyotter

Ah, you're making the mistake of dividing 14 squared by six thirds instead of multiplying them.

39. anonymous

ook

40. anonymous

v=392

41. nerdyotter

Good! :) Now, to calculate percent change, you would start by finding the difference between the two volumes (or the increase). The formula to find the increase is... $Increase = New - Old$

42. nerdyotter

In this case, it would be Pyramid B - Pyramid A.

43. nerdyotter

Er, I apologize. The other way around, I believe.

44. anonymous

3,136-392= 2744

45. anonymous

^^

46. nerdyotter

Then, the formula to find percent change is $change = (\frac{ increase }{ original })(100)$

47. anonymous

2744 2744/3136 (100)

48. anonymous

87.5% is that correct

49. anonymous

@nerdyotter is this correct

50. anonymous

before u leave