JamenS 3 years ago A motor scooter purchased for \$1,000 depreciates at an annual rate of 15%. Write an exponential function, and graph the function. Use the graph to predict when the value will fall below \$100.

1. Traxter

You must be able to start this one off for yourself. Can you show us what you have so far?

2. JamenS

1000(1.15)=100?

3. hal_stirrup

hi

4. JamenS

hi

5. JamenS

can u help me :)

6. hal_stirrup

ok ask you self . what is the value of motor scooter after 1 year?

7. JamenS

150\$....

8. JamenS

?

9. hal_stirrup

no

10. hal_stirrup

so what the question is really saying is , the value of motor scooter goes down by 15%.

11. SNSDYoona

100 = 1000e^(-0.15t)

12. JamenS

850\$

13. hal_stirrup

@SNSDYoona we dont give answers out like that.

14. SNSDYoona

1000 = the starting money that u purchased it the basic formula for this exponential decay and growth functions is A= Ye^(kt)

15. SNSDYoona

thts why i give him the answer first to see if he does any calculation wrong then explain to him if he doesnt get it

16. hal_stirrup

thats why we don't give answers out. you need to explain the exponential formula. Not just stated it!!!

17. SNSDYoona

A = the amount u left after a certain period of time Y = initial amount started with k = ur rate of decay/growth t= the time

18. JamenS

0.1=(-0.15t)

19. JamenS

?

20. SNSDYoona

have u learn natural logs?

21. SNSDYoona

from 100 = 1000e^(-0.15t) u simplify it then u get down to 0.1= e^(-0.15t) then u take the natural logs off both side u get ln(0.1) = -0.15t then u solve for t ln(0.1)/0.15 = t

22. JamenS

i got 0.666

23. SNSDYoona

u shud get 15.35

24. SNSDYoona

use ur calculator.. did u type in correctly?

25. JamenS

i divide .1 by .15?

26. SNSDYoona

nonono u use ln << ln = natural log

27. SNSDYoona

look at ur calculator and search for ln

28. SNSDYoona

press ln and then (0.1)

29. SNSDYoona

then divide by (-0.15)

30. JamenS

im using google calculator i dont have 1

31. JamenS

15.3?

32. SNSDYoona

yeap

33. JamenS

v(t) = 0.85(1000)t; the value will fall below \$100 in about 18 yr. v(t) = 1000(0.85)t; the value will fall below \$100 in about 18 yr. v(t) = 0.85(1000)t; the value will fall below \$100 in about 14.2 yr. v(t) = 1000(0.85)t; the value will fall below \$100 in about 14.2 yr.

34. JamenS

u still there

35. cnn1999

hi

36. LiamMcBay

hi