In: Finance
Critical Thinking Questions
1]
As per rule of 72, the number of years required for $1 to double in value is approximately (72 / interest rate).
For example, at 8% interest rate, the number of years required for $1 to double in value is (72 / 8%) = 9 years
This is verified as below :
future value = present value * (1 + interest rate)number of years
$2 = $1 * (1 + 8%)9
2 = 2
2]
Compounding is when the interest in each period is added to the original principal such that the principal at the end of each period is increased. That is, the original principal does not remain fixed (as in the case of simple interest) but keeps increasing as the interest in each period is added to the original principal. This leads to "compound growth" which results in a much higher interest in each subsequent year.
Discounting is the opposite of compounding. A future value is discounted such that its present value is calculated after the effect of compound interest. That is, the present value, if invested at compound interest, results in the ending future value
3]
An annuity is a series of payments that occur periodically (yearly, monthly, weekly etc).
For example, a sum of $100 received after 1 year is not an annuity, but a lump sum.
A series of $100 payments received every month for 12 months is an annuity
4]
In an ordinary annuity, each payment is received at the end of the period.
In an annuity due, each payment is received at the beginning of the period.
Future value of annuity = P * [(1 + r)n - 1] / r,
Future value of annuity due = P * (1 + r) * [(1 + r)n - 1] / r,
PV of annuity = P * [1 - (1 + r)-n] / r,
PV of annuity due = P + [P * [1 - (1 + r)-(n-1)] / r]
where P = periodic payment
r = interest rate per period
n = number of periods