# Thread: Exponential Growth and Decay Help?

1. ## Exponential Growth and Decay Help?

I need help with part c (mainly with how fast the salt is dissolving) and d please, any help would be appreciated. Thanks.

2. ## Re: Exponential Growth and Decay Help?

When you're finding the rate, or how fast or slow something is, you use the derivative expression.

so for c)
you find dS/dt and then sub in t = 5 and your value of k from part b), that's your rate.

d)sub S = 4 (as that's the amount that's left undissolved ) and your k from b)

Then you solve for t, assuming you have you the logarithm knowledge to work out the algebra.

3. ## Re: Exponential Growth and Decay Help?

Originally Posted by integral95
When you're finding the rate, or how fast or slow something is, you use the derivative expression.

so for c)
you find dS/dt and then sub in t = 5 and your value of k from part b), that's your rate.

d)sub S = 4 (as that's the amount that's left undissolved ) and your k from b)

Then you solve for t, assuming you have you the logarithm knowledge to work out the algebra.
Thanks.

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