## Elise_a18 one year ago Medal and Fan Not a multiple choice question, test, or Exam question What is the formula for finding the height of a square pyramid who's volume is 8 cubic feet and a base length of 2 ft?

1. Elise_a18

@vera_ewing @Voltage @Vocaloid

2. Vocaloid

good, so we have V = (1/3)(r^2)(h) we have V and r, and we want to find h

3. Elise_a18

yep:)

4. Vocaloid

so we re-arrange our formula to get h = 3V/(r^2) now plug in V and r

5. Elise_a18

I'm having a heard time isolating h

6. Vocaloid

ok, want me to walk you through it?

7. Elise_a18

Oh! wait!

8. Vocaloid

nope, this formula works for a square pyramid a cone would be (1/3)(pi)r^2h

9. Vocaloid

if r = the side length of the base, that is

10. Elise_a18

Alright, let's start again. I have 2 formulas for a square pyramid $\frac{ 1 }{ 6 } (b^3)$ and $\frac{ 1 }{ 3 } (b) (h)$

11. Vocaloid

hm... the first formula only works if the height is equal to the side length of the base

12. Vocaloid

lets use the second formula V = (1/3)bh where b is the area of the base and h is the height

13. Elise_a18

|dw:1444411817781:dw|

14. Elise_a18

Okay so the formula would be $\frac{ 1 }{ 3 } (2) (h)$

15. Vocaloid

oh, ok, if 2 is the area of the base, then yes

16. Vocaloid

V = (1/3)(2h) now multiply both sides by to "get rid of" the 1/3

17. Elise_a18

base length rather :P

18. Elise_a18

@Vocaloid

19. Vocaloid

wait, why "cubic feet"? that implies 3 dimensions

20. Vocaloid

if the side length is 2, then the base is 4

21. Elise_a18

yeah, it's a square pyramid. like in my drawing

22. Elise_a18

Ohh right! I forgot that BL= S^2

23. Vocaloid

right, so if b = 4 then V = (1/3)(4)(h) know how to isolate h now?

24. Elise_a18

Yeah I did it on my white board. Would it be h= $\frac{ 1 }{ 3 } *8\frac{ 4 }$

25. Elise_a18

oh. O-o

26. Vocaloid

nope, not quite

27. Elise_a18

|dw:1444412375012:dw|

28. Vocaloid

we want to "get rid of" the 1/3 fraction so we multiply both sides by 3

29. Elise_a18

not like this?

30. Vocaloid

V = (1/3)(4)(h) 3V = 4h with me so far?

31. Elise_a18

yes. So it would be V=8 right? because the vol is already given?

32. Elise_a18

OH! it's 6?

33. Vocaloid

nope, remember, we want to find h

34. Vocaloid

3V = 4h now divide both sides by 4

35. Elise_a18

i though we need to divide 3V by 4 to isolate h?

36. Vocaloid

right

37. Vocaloid

h = 6, right

38. Vocaloid

39. Elise_a18

Yeay! Thank you so much! I know I'm kinda slow but I love it when I can actually understand X)

40. Elise_a18

i was seeing that V is substituted by 8