Formula for continuously compounding interest발음듣기
Formula for continuously compounding interest
We're going to compound four times a year\ - or every three months And let's say that our interest rate - if we were only compounding once per year - would be 10%.발음듣기
But since you're going to compound four times a year, what we're going to see in an expression is that we're going to divide this by 4 to see how much we compound each period.발음듣기
And I encourage you actually to pause this video and try to write an expression for the amount you would have to pay back if you were to do this.발음듣기
If you were to borrow $50 over three years, compounding 4 times a year, each period, you would be compounding 10% divided by 4%.발음듣기
And you're going to multiply that - So you're going to compound it. each time, each period, each of these 3 x 4 periods. You have 3 years.발음듣기
We'll write that as a decimal: 0.10. divided by the number of time that you're compounding per year - to the - (Well, you'd be raising it to the nth power if this was only over 1 year.) So there are 4 periods.발음듣기
So you're going to be doing this three - you're going to have 4 periods 3 times. Let me write this.발음듣기
I encourage you, if you want, you could pause the video and you can use your calculator to actually calculate what that is.발음듣기
You're going to be growing it by 2 1/2% and you're going to do this 12 times, because there's 12 periods. periods per year times 3 years.발음듣기
If we wanted to write this in a little bit more abstract terms, we could write this as P(1 +).발음듣기
You could pick your P, your Ts, your Ns and your Rand you could put it here and that's essentially how much you're going to have to pay back.발음듣기
An interesting thing, and you saw that we had this up here from a previous video, where we took a limit as N approaches infinity.발음듣기
If we took the limit as N approaches infinity, if we took the limit of this as N approaches infinity, what is this conceptually?발음듣기
You could really say, "This would be the case where we're doing continuous compound interest.발음듣기
You're dividing your time period in an infinite number of chunks and then compounding just an infinitely small extra amount every one of those periods.발음듣기
As we see, that this actually doesn't just go unbounded and give us crazy things, that we can actually use this to come up with a formula for continuously compounding interest.발음듣기
Which is used heavily in finance and banking and, as you can imagine, a bunch of things, actually many things outside of finance and banking, exponential growth, etc., etc.발음듣기
I'm going to say that X is the reciprocal of R over N, so that I can get a 1 over X right over here.발음듣기
We're just assuming that that's a given, that N is what we're really seeing what happens as we change it.발음듣기
I'm not being as super rigorous, but it's really to give you an intuition for where the formula we're about to see comes from.발음듣기
This is the same thing. This is equal to P times(let me put some parenthesis here)times (maybe that's too big) times the limit.발음듣기
If I raise something to the product of these, I'm taking X x R x T, that's the same thing as doing this whole thing to the X and then raising that to the RT power.발음듣기
I'm doing a couple of steps in the process here, but hopefully this seems reasonably intuitive for you.발음듣기
This is the same thing as the limit as X approaches C of F of X to the X and then all of that raised to the RT power.발음듣기
If we continuously compound, we're going to have to pay back our principal times E, to the RT power.발음듣기
If you were to borrow $50, over 3 years, 10% interest, but you're not compounding just 4 times a year, you're going to compound an infinite times per year.발음듣기
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