# rate of chanceWatch

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#1
hi, can somebody check this please

the volume of a sphere is increasing at the rate of 200 cm
find in terms of pi the rate of increase of the radius when the radius is 5

dv/dt = 200

dr/dt = dv/dt x dr/dv

formula for volume of a sphere 4/3 x pi x r^2
differential = 4 x pi x r^2

200 x 4 x pi x r^2
r=5
200 x 4 x pi x 25 = 20,000 pi

seems too big to be correct..
0
5 years ago
#2
(Original post by hatsuko)
hi, can somebody check this please

the volume of a sphere is increasing at the rate of 200 cm
find in terms of pi the rate of increase of the radius when the radius is 5

dv/dt = 200

dr/dt = dv/dt x dr/dv

formula for volume of a sphere 4/3 x pi x r^2
differential = 4 x pi x r^2

200 x 4 x pi x r^2
r=5
200 x 4 x pi x 25 = 20,000 pi
Do you think that these are the same thing?
0
#3
(Original post by TenOfThem)
Do you think that these are the same thing?
not sure, i have no idea what these things mean tbh
0
5 years ago
#4
(Original post by hatsuko)
not sure, i have no idea what these things mean tbh
Are you doing A Level Maths?
0
#5
(Original post by TenOfThem)
Are you doing A Level Maths?
yes
0
5 years ago
#6
(Original post by hatsuko)
yes
In Y13?

If so

Surely you know what and mean

And, surely you know that the next line of working to should have started with one of them rather than "differential"
0
#7
(Original post by TenOfThem)
In Y13?

If so

Surely you know what and mean

And, surely you know that the next line of working to should have started with one of them rather than "differential"
i am in y13, but I don't know what they mean
and i'm guessing it should be dr/dv
0
5 years ago
#8
(Original post by hatsuko)
i am in y13, but I don't know what they mean
Then you need to speak to your teacher

This is a basic understanding of what the derivative means
0
#9
(Original post by TenOfThem)
Then you need to speak to your teacher

This is a basic understanding of what the derivative means
0
5 years ago
#10
(Original post by hatsuko)
I have a feeling that was not well defined for you in Y12

However, it is shocking if the differential function has not been explained as a rate of change now that you are doing this work
1
#11
(Original post by TenOfThem)
I have a feeling that was not well defined for you in Y12

However, it is shocking if the differential function has not been explained as a rate of change now that you are doing this work
well, our AS teacher was pretty ... crap
1
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