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logarithmic functions help?
solve the equation algebraically.
2,000(1.2)^(t/5) = 20,000
Solve for t.
Any help would be great! I think I got to use log, but I have no idea how to use log on my calculator. If anyone could tell me how, that would be great! I got the TI-84 Plus, if that means anything.
2 Answers
- ChrisLv 77 years ago
2000(1.2)^(t/5) = 20000
(1.2)^(t/5) = 20000/2000 = 10
(t/5)lg1.2 = lg10
[Put 1.2 in you calculator and press the log key. You will see 0.0792.]
[You could do the same for 10, but the answer is 1 anyhow.]
(t/5)(0.0792) = 1
t = 5/0.0792 = 63.1
- GMTLv 67 years ago
2,000(1.2)^(t/5) = 20,000
........................................ Divide by 2000
(1.2)^(t/5) = 10
........................................ Put into logarithmic form
log(1.2)10 = t/5
........................................ Multiply both sides by 5
5 log(1.2)10 = t
........................................ Change to base 10 using logarithmic change of base formula.
5 log10 / log 1.2 = t
........................................ Since log(10)10 = 1, substitute it.
t = 5 / log 1.2
The answer is in base 10. Now you can enter this into your TI-84.
Just type in
5/log(1.2)=
I hope this helps!
