# Integration/differentiation

• April 17th 2008, 03:12 AM
mucky
Integration/differentiation
Only just started inegration and differentiation and to top it off, the queston
has totally thrown me off track, any help through the steps would be greatly appreciated.

The number of sales, S, in 000's of a phone is given by the formula:
S=Ae^kt

where t is time in weeks after the launch. In the week leading to the launch
3000 phones are ordered (ie when t = 0 then S = 3000)

In the fifth week (ie at t = 5) 5000 are sold.

(i) find A and k

(ii)predict, according to this model, what the phone sales will be after 7
weeks.

(iii) How long will it take to reach 20000 per week?

thankks
• April 17th 2008, 03:13 AM
mucky
S=A.℮^k.t)
• April 17th 2008, 03:43 AM
Mathstud28
Quote:

Originally Posted by mucky
Only just started inegration and differentiation and to top it off, the queston
has totally thrown me off track, any help through the steps would be greatly appreciated.

The number of sales, S, in 000's of a phone is given by the formula:
S=Ae^kt

where t is time in weeks after the launch. In the week leading to the launch
3000 phones are ordered (ie when t = 0 then S = 3000)

In the fifth week (ie at t = 5) 5000 are sold.

(i) find A and k

(ii)predict, according to this model, what the phone sales will be after 7
weeks.

(iii) How long will it take to reach 20000 per week?

thankks

It is exponential growth/decay since $y=Ce^{kt}$ we put t=0 when s=3000 to get $3000=Ce^{k\cdot{0}}\Rightarrow{C=3000}$..now continue with that until all the variables are found then just plug and chug
• April 17th 2008, 03:10 PM
mucky
helppp...plz
Thabks for help but I am still misunderstanding how to find A and k....Please someone help me out
thankyou........(Worried)