Find n

frctl

Full Member
Joined
Jun 29, 2019
Messages
252
The question:
Use the compound interest formula to find n to the nearest larger integer value.

Given:
A = 2P; i = 0.06; n = ?

My work:
A = P(1 + i)n
2P = P(1 + 0.06)n
2 = (1 + 0.06)n

How do I solve for n in this case?
 
Try using logs. What happened to t and dividing r by n? Please try posting the entire problem including how long it will take to have 2P and the value for t.
 
Last edited:
You solved your equation correctly by getting n = ln(2)/ln(1.06) ~ 12 NOT 12.

The problem is that you did not use the correct formula.

Is P ( 1+ .06/12)12*1= 2P. The answer is no.

How long is it supposed to take to go from P to 2P? That needs to be part of the equation so the equation knows how many times the amount get compounded.

The formula is A = P (1 + r/n)nt where you want A to be 2P
 
Touchy, @Jomo.

Do it like this.
The question:
Use the compound interest formula to find n to the nearest larger integer value.

Given:
A = 2P; i = 0.06; n = ?

My work:
A = P(1 + i)n
2P = P(1 + 0.06)n
2 = (1 + 0.06)n

How do I solve for n in this case?
[MATH]2P=P(1+0.06)^2[/MATH]
[MATH]2=(1+0.06)^2[/MATH]
Now where will you take the log from?
 
Touchy, @Jomo.

Do it like this.

[MATH]2P=P(1+0.06)^2[/MATH]
So you are saying that if you deposit money into an account that gets compounded twice that the money will double? Wow. Beside, if n~12 why are you replacing n with 2?
You can't figure out n until you know how long it will take to double?

Think about it. I deposit $1000 at 8% interest. I ask you how many times does the interest need to be compounded per year in order to have $2,000. You need to know how long I am willing to wait before you can answer that.
 
To OP: Please please post the entire problem. That will get you the best help. An image of the problem will be the best.
 
So you are saying that if you deposit money into an account that gets compounded twice that the money will double? Wow. Beside, if n~12 why are you replacing n with 2?
You can't figure out n until you know how long it will take to double?

Think about it. I deposit $1000 at 8% interest. I ask you how many times does the interest need to be compounded per year in order to have $2,000. You need to know how long I am willing to wait before you can answer that.
That's the problem that OP wrote.
 
You solved your equation correctly by getting n = ln(2)/ln(1.06) ~ 12 NOT 12.

The problem is that you did not use the correct formula.

Is P ( 1+ .06/12)12*1= 2P. The answer is no.
You're assuming monthly compounding. Where were we told that?

I'm assuming the problem is exactly as given.

@frctl, please show us the actual problem, if you didn't.
 
You're assuming monthly compounding. Where were we told that?

I'm assuming the problem is exactly as given.

@frctl, please show us the actual problem, if you didn't.
I actually did not assume monthly compounding. I was just using the 12 that the OP found for n.
 
You're assuming monthly compounding. Where were we told that?

I'm assuming the problem is exactly as given.

@frctl, please show us the actual problem, if you didn't.
Dr Peterson, why would we not have to use the compound interest formula? If somehow the OP did, then how can that be. Isn't it true to know how many time the funds needs to be compounded depend on the number of years it is to take to double. What am I missing?
 
You said yourself that 12 was incorrect.
Yes, I did say that n~12 is not correct. I said Is P ( 1+ .06/12)12*1= 2P? The answer is no. I tried using n=12 as the OP stated is the answer. I may be wrong but I never said that 12 was the answer.
 
Top