Question

3-d coordinate plane geometry. Check my work?

Answer 1

pyramid V = 2666
Triangular prism SA = 72

I had trouble on both and I want to know if I did them correctly.

Answer 2

volume of a cone is 1/3 the area of its representative cylindar ... or in this case, 1/3 of its representative cube/box

Answer 3

and a prism is just the base area times its height/length

Answer 4

that pyramid is awful to try to read tho ... i would suggest creating a similar, smaller pyramid by dividing it all by 10

Answer 5

scale it and stand it upright

Answer 6

i think i see the 3 off alitlle, 3+5 = 8, so 8 tall

Answer 7

scale it back to get:

100*100*80 for the box, and divide it by 3

Answer 8

I'm pretty sure I've got the volume for the 1st pyramid; I did something wrong, but I re-did it the height is 80 , b 100x100 so it should be 1/3 b x h = ... err yeah you said it before I did.. XD

Answer 9

second one I'm still struggling with, I've got all the measurements for the triangle but no the rectangle. triangles length 4, base 3, height 4. I can get the volume just fine but not the surface area.

Answer 10

266,666 and 2/3 is what i get for the pyramid i think you cut off some of your 6s

Answer 11

I think what I did first time is I only did 100 x 80 instead of 100x100

Answer 12

right :)

Answer 13

for the prism, it might be easier to read if we move the point E to the origin: move everything by (-4,0,-1)

D' = 0,0,4
E' = 0,0,0 A' = 0,3,0

in the zy palne that give us a 3x4 base triangle with an area of 6

Answer 14

the length along x is from Dx to Cx = 4

Answer 15

Is point F even important? I never really added it into what I was working on.

Answer 16

if you are calling F that point in the back, then its not important; it simply relates the front base and the back base. we only have to define the area of one of the bases

Answer 17

yeah, the one below C.
that's what I thought, so okay, I'm not missing anything..

point A->B is 4; so..

Answer 18

we could have used F if we wanted to, and moved F to the origin; moving the others by (0,0,-1) still results in a zy plane triangle of 3x4

Answer 19

in any event .. 72 aint it :)

Answer 20

yeah, that's what I figured. never been good with surface area.

Answer 21

surface area? ugh, i was doing volume :/

Answer 22

2 bases at 6
a side at 3x4
a side at 4x4
a side at 5x4

12+12+16+20

Answer 23

oh ok so I did use the wrong formula
it's the wh + lw + lh + ls

Answer 24

I think.. I have so many numbers on my paper. @_@

Answer 25

not sure about the formula, i never like to rely on those things to much :)

Answer 26

I ended up with 2 answers; 63 and 72

Answer 27

side: 5x4 = 20
side: 4x4 = 16
side: 3x4 = 12
bases ...... 12
-------------
Sa = 60

Answer 28

so.. I'm probably just bad at math if I did it wrong twice.. haha

Answer 29

thank you very much though for your time, xyz stuff always freaks me out, so now I sorta know what to do on my finals.. :D

Answer 30

:) we all have our awkward moments

Answer 31

good luck