Question

Can someone see if i'm doing this right ?
The formula : F=P(1+r/n)^nt
Odessa deposited $1,347.80 into a savings account with an interest rate of 3.3% compounded monthly. About how long will it take for the account to be worth $5,000?
F=1,347.80
P=5,000
N=12
R=3.3% 0.033

1,347.80(1+0.033/12)^12t ?

Answer 1

I menat 1,347.80=5,000(1+0.033/12)^12t

Answer 2

You were on the right track in that last line in your problem statement. You would set that equal to 5000 and then take logs.

Answer 3

In your last post, you need to switch the positioning of those 2 dollar amounts. This is because 5000 is what you end up with, not what you start out with.

Answer 4

Is this starting to make sense now, @NaCl ?

Answer 5

no i'm a visual leaner .

Answer 6

wait

Answer 7

5000=1347.80(1+0.033/12)^12t ?

Answer 8

Yes! You've got it now!

Answer 9

http://www.wolframalpha.com/input/?i=5%2C000%3D1%2C347.80%281%2B%280.033%29%2F%2812%29%29%5E12t

Answer 10

An easy way to think about the 2 dollar amounts is to see what happens to the deposit of "one dollar". You would put "1" where you have 1347.80 and see what it grows to.

Answer 11

would it be 39 years, 10 months ?

Answer 12

In that wolfram equation, you have to put 12t in parentheses because exponentiation takes precedence over multiplication.

However, you did get the right answer with:

39.780788780031041623654225812091

Good job!

Answer 13

Good luck to you in all of your studies! @NaCl

Answer 14

Sonya currently has an account balance of $1,533.43. Her initial deposit on the account was $962 and it earned 3.3% simple interest. How long has Sonya held the account?

30 years

11 years

48 years

18 years

Answer 15

simple interest is

Interest = Principal * rate * time

to do your problem, figure out how much interest Sonya received
(total - start)

then solve for time in the above equation

Answer 16

@phi I did I=962*3.3%*48=1523.808 ?

is 48 years right ?

Answer 17

that would be the amount of simple interest you get after 48 years
the amount in the account would be the interest plus how much you start with.

Step 1:
if you start with 962, and after some years have 1,533.43
how much interest did you get ?

Answer 18

3.3 %

Answer 19

that is a rate. Think like this: you start with 1 apple, and some time later you have 3 apples. How many apples were added ?

Answer 20

Step 1:
if you start with 962, and after some years have 1,533.43
how many dollars were added to the account?

Answer 21

o.O idk

Answer 22

Your end account balance is 1533.43 where you started with 962, giving you

571.43 total interest because 1533.43 - 962 = 571.43

That means 962 dollars generated 571.43 dollars in interest. Each dollar generated:

571.43 / 962 = 0.594002079 dollars in interest

(0.033) times (t years) = 0.594002079

t = 0.594002079 / 0.033 = 18 years

Answer 23

are you saying you can't figure out how much bigger 1533.43 is than 962?

Answer 24

as tcarroll shows, you get 571.43 in interest
because 962 + 571.43= 1533.43

now you can use the formula
Interest= Principal * rate * time
571.43 = 962* 3.3% * t to solve for t

Answer 25

This explanation of @phi s is really good. It's basically the same as mine. I added a step which may or may not be necessary that has to do with what one dollar generates in interest. I tend to do that because it is rather fundamental to consider one dollar.

Answer 26

Anyway, @NaCl you can look at my post of 2 previous to see how I arrived at 18 years.

Answer 27

Thank you both for you time @tcarroll010 @phi

Answer 28

You are very welcome! Anytime! If you are ok now with these 2 problems, then close it when you are ready, and if you have any new problems, just start a brand-new thread. Otherwise, if you are still in need of any further explanation on this problem, we can still kick it around.