Question

Volume= 18 cm3
Height of the pyramid= 3 cm
B1= 2 cm
B2= 3 cm
What is the height of the base?

Answer 1

you mean area of the base?

Answer 2

wait, no. base area is .5xh(b1+b2) so i need the height

Answer 3

i though height was given as 3 cm?

Answer 4

thats the height of the pyramid

Answer 5

okay, and what do you need to evaluate?

Answer 6

the height of the base

Answer 7

http://en.wikipedia.org/wiki/Pyramid_(geometry)
are you talking about that?
how is there a height of the base?

Answer 8

x=18cm3

Answer 9

ah, so you should say its a trapezoidal pyramid.

Answer 10

yes

Answer 11

okay, do you know the formula to the volume of a pyramid?

Answer 12

yes. 1/3 x B x H

Answer 13

what is B in the formula?

Answer 14

i dont know. b1 = 2 cm b2= 3 cm

Answer 15

yess.

Answer 16

okay you must always know what the letters mean in a formula.
for example the area of a rectangle is the its length multiplied by its width. you shouldn't remember it as l x b, because when I ask you what l and b are, you don't have an answer to that.

Answer 17

volume of a pyramid is one-thirds the product of the base area and its height

Answer 18

yea

Answer 19

so B is the area of the base.
right,
so substitute H and V in the equation

Answer 20

right

Answer 21

soooo,,,,,,,,,,,,,,,,,,,,

Answer 22

so, tell me what you got after substituting the values of V and H.

Answer 23

V= 18cm H= 3cm. h= i dont know

Answer 24

substitute V = 18, H =3 in
V = 1/3 x B x H and find the value of B.

Answer 25

but H is the height of the pyramid, i need the height of the base (h)

Answer 26

Yes, volume of a pyramid is 1/3 x Base area x Height of the pyramid.

so once you find the base area of the pyramid, substitute its value as 1/2(b1+b2) x h and find h

Answer 27

so how do you find h?

Answer 28

I just told you.
can you please just for the love of god substitute
V and H in
V = 1/3 B x H and give me an answer for B?

Answer 29

BUT I DONT KNOW THE BASE. sorry i'm not good at math, my lord.

Answer 30

what is so hard about this?
18 = 1/3 x B x 3
B =18
but we know that B = 1/2(b1+b2) x h
so 18 = 1/2(2+3) x h
h = 36/5

Answer 31

you just have to work backward to get the base. you won't always find equations in the correct order. you must know how to manipulate equations to get your variable.

Answer 32

where did we get 36

Answer 33

multiply 18 by 2 and divide by 5.

Answer 34

i got h = 7.2. is this correct?

Answer 35

yeah. oooo you used a calculator to find the value of 36/5! good on you!

Answer 36

btw, which grade are you in?

Answer 37

7th

Answer 38

okay. Have you ever done manipulation of equations?

Answer 39

no

Answer 40

like if x = y+2, what is y?

Answer 41

x-2?

Answer 42

then why do you say you haven't done any algebraic manipulation before?

Answer 43

btw, h= 2.4. 1/2 x 2.4 (3+2) = 6. 6x3=18.

Answer 44

why do you say 6 x 3 = 18?

Answer 45

is the formula for volume of a pyramid area of base x height?

Answer 46

because the height of the pyramid is 3 cm, so to find the volume you have to multiply the base by the height.

Answer 47

oh yeah, divide by 3. nevermind...

Answer 48

good, at least you figured that out on your own.

Answer 49

oh stopp

Answer 50

:D