Question

The volume of a cube is increasing at a rate of 10cm^3/min. How fast is the surface area increasing when the length of the edge is 30cm.

Answer 1

whats the formula for volume of cube?

Answer 2

V=a^3

Answer 3

here rate is given so what u do ?

Answer 4

find the derivative with respect to the rate? ;/

Answer 5

exactly :) proceed

Answer 6

;O that was right?!

Answer 7

cntinue :)

Answer 8

V'=3a^2(d/dr)...?

Answer 9

If your final is tmrw, I think u should focus on optimization and how to sketch a graph. Guarantee'd those will be worth more points.

Answer 10

I'm going through everything on the study guide, I have until 7pm tomorrow.. it's 2am. thanks though. But, I have time to cover everything

Answer 11

There will be no sketching a graph either. It's on a scantron.

Answer 12

@AravindG did i do that wrong or?

Answer 13

srry i was away

ya u r right

Answer 14

So now, I plug in right?

Answer 15

yep

Answer 16

a=30?
d/dr=10?

Answer 17

do u have final answr?

Answer 18

I'm not getting the right answer

Answer 19

whats the answr u have?

Answer 20

3(30^2)(10)=27,000

Answer 21

hey u dont have dr/dt !!

Answer 22

V'=10?

Answer 23

3a^2(d/dr(t))=10
from that find dr/dt

Answer 24

1/270?

Answer 25

now using that da/dt and the diff of area ie 2adr/dt

Answer 26

2ada/dt will give u the answer :) srry gtg

Answer 27

.... I'm so lost

Answer 28

i think @Outkast3r09 will take over bye :)

Answer 29

alright first figure out what you're trying to find the rate of

You're looking for the surface area and you're given the rate of volume... you have to write Surface area in terms of V

Answer 30

so what is the equation for surface area of cubes?

Answer 31

omg!..... 6a^2

Answer 32

SA=6a^2

Answer 33

alright so \[SA=6a^2\]

however you ned this equation for volume hmmmmm

Answer 34

volume is \[x^3\]

\[v=x^3\] if we solve for one side you get