Question

At an interest rate of 7% compounded annually, how long will it take to double the following investments? (Round your answer to the nearest year.)
(a) $200
_____ years

Answer 1

JIMMY!

Answer 2

:D

Answer 3

hi - the real me is there today!

Answer 4

i noticed

Answer 5

can you help me with this?
this is the formula p(1+r/n)^nt
ive done problems like this but this ones missing info that i usually have given

Answer 6

i'm a bit rusty at these
what is n ? t = number of years right?

Answer 7

r = 7/100 = 0.07

Answer 8

n is 1 because it says its compounded annually and t is the years which is what i'm looking for

Answer 9

this is what i get 200(1.07)^t

Answer 10

then what?

Answer 11

ok so the formula must be

400 = 200(1 + 0.07)^ t

Answer 12

400 because you have doubled your money

Answer 13

i see... i left the 400 out

Answer 14

so (1 + 0.07)^ t = 400/200 = 2
1.07^t = 2

Answer 15

yeah and then?

Answer 16

now you can take logs:

log 1.07^t = log 2
t * log 1.07 = log 2

Answer 17

t = log2 / log 1.07
= 10.24

Answer 18

thats 10 years

Answer 19

thats right but could u put the last few steps into words please

Answer 20

ok you see how i got
1.07^t = 2 ?

Answer 21

yes

Answer 22

then take the logs of both sides

Answer 23

so we have log 2 = t * log 1.07

Answer 24

then?

Answer 25

right
then divide both sides by log 1.07
to get
t = log 2 / log 1.07
- then use your calculator

Answer 26

Ok gotcha! Thanks!

Answer 27

ok
:D