Question: What is the significance of the 0 in the formula for simple interest?

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In summary, Simple Interest is defined as a function in Mathworld, represented by a(t) = a(0)(1 + rt), where a(t) is the sum of principal and interest at time t for a constant interest rate r. The 0 in a(0) represents the function evaluated at t=0, which is the principal amount. This is not a multiplication by 0, but rather a representation of the function at a specific time.
  • #1
catch.yossarian
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In Mathworld, they define Simple Interest as:

a(t) = a(0)(1 + rt)

where a(t) is the sum of principal and interest at time t for a constant interest rate r.

I just want to know why that 0 is in there. Anything divided by 0 will be 0, thus a(t) = 0?
 
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  • #2
I would imagine that a(0) is the principle as it is the sum of the principle and the interest at t=0. Since there is no interest at t=0 the sum of the principle and the interest would be the principle.
 
  • #3
Anything divided by 0 is undefined...

They're saying a(t) is a function and a(0) is that function evaluated at t=0.

It would be more clearly written a[t] = (1 + rt)*a[t=0]

cookiemonster
 
  • #4
In other words, the "a(0)" is not "a times 0", it is "the function a(t) evaluated at t= 0".
 
  • #5
HallsofIvy said:
In other words, the "a(0)" is not "a times 0", it is "the function a(t) evaluated at t= 0".
And in still more words (well, actually less words), "a(0)" is the principal.

Ironic - I was just looking for this formula so I could buy a car...

edit: oops - they don't use that formula.
 
Last edited:
  • #6
Russ,

If you're talking about the depreciation curve, I think that's exponential, not linear.

Edit : No, you're calculating payments, aren't you. I think that's compounded.
 

Related to Question: What is the significance of the 0 in the formula for simple interest?

1. What is interest a(t) = a(0)(1 + rt)?

Interest a(t) = a(0)(1 + rt) is a mathematical formula used to calculate the amount of money earned on an initial investment over time. It takes into account the principal amount, the interest rate, and the time period.

2. How is interest a(t) = a(0)(1 + rt) calculated?

The formula for calculating interest a(t) = a(0)(1 + rt) is: a(t) = a(0) + a(0)rt, where a(t) is the final amount, a(0) is the initial amount, r is the interest rate, and t is the time period.

3. What is the difference between simple interest and compound interest?

Simple interest is calculated only on the initial investment amount, while compound interest takes into account both the initial investment amount and the accumulated interest. This means that compound interest earns interest on interest, resulting in a higher overall return.

4. How does the interest rate affect the final amount in the formula a(t) = a(0)(1 + rt)?

The interest rate (r) is a key factor in the calculation of the final amount (a(t)). A higher interest rate will result in a larger final amount, while a lower interest rate will result in a smaller final amount. This is because a higher interest rate means the investment is growing at a faster rate over time.

5. Can interest a(t) = a(0)(1 + rt) be used for any type of investment?

Interest a(t) = a(0)(1 + rt) can be used for any type of investment that earns a fixed interest rate over time, such as a savings account or a bond. However, it may not be accurate for investments with variable interest rates or investments that involve other factors, such as stock prices.

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