Related Rates- Cubic Crystal

wind

Junior Member
Joined
Sep 20, 2006
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179
A cubic crystal is being grown as a science experiment.

a) if the sides of the crytal are increasing in size at a rate of 0.01 mm/s, how fast is the volume of the crytal increasing when its sides are 2.3 mm long?

b) if the value of the cyrstal is $4/mm^3, how fast is the value of the cyrstal increasing when its sides are 2.7 mm long?

a) ds/dt = 0.01 mm/s
dv/dt = ? when 2.3 mm
dv/ds = s^3

dv/dt = (dv/ds)(ds/dt)
= (dv/ds s^3)(0.01)
= (3 (2.3^2)(0.01)
= 0.1587

b) dc/ds = 4
dc/dt = ? when 2.7 mm
dc/dt = (dc/ds)(ds/dt)
= (4)(0.01)

but then there is no variable so I think I did this wrong. Can someone help me with this question? Thanks.
 
\(\displaystyle \L\,Volume(t) = k*[Side(t)]^{3}\)

\(\displaystyle \L\,dVolume/dt = 3*k*Side^{2}*ds/dt\)

Now try it.
 
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