Interests Flashcards
Simple interest =
Any money saved that receives an interest payment at the end of each period which is NOT REINVESTED
SI = P × (i/100) × t
SI = Simple Interest
P= Principal (initial amount)
i = rate of interest (as a percentage)
t = number of time periods
Compound interest =
Any money saved then receives an interest payment which is then REINVESTED.
(Most types of account receive (or pay) compound interest (CI).)
At = P× (1+ i)t
At = Amount after t time periods P = Principal or sum invested i = compound interest rate (as a decimal)
t = end of time period in question
Compounding factor =
(1+i)t
Formula for total compound interest paid
We merely take the end value after period t (At) and substract the initial amount P to find the total compound interest paid over this time period.
CIt = At - P
CIt = P(1 + i)t - P
Detailed table of At = P(1 + i)t for P=100, t=5(years) and i=0,1
(example in slide)
P=100
i=0,1
Interest Rate has to be expressed as …
A rate per unit interval of time.
It is not restricted to one year: could be a half-year, a quarter of a year, an hour or any other time interval
Effective Rate of Interest =
The actual rate of accumulation over the stated time interval. (when compounding)
Nominal Rate of Interest =
The nominal rate is the stated interest rate for a unit interval of time, which may be different from that used for accumulating interest, e.g.:
– 3% per half-year would be quoted as being “6% per annum, payable half-yearly”.
Let r be the nominal rate of interest per annum that is payable x times a year.
• The equivalent or effective rate of interest per annum ( i ) is given by:
The accumulated amount of an investment (P) at a nominal rate of interest per annum, payable x times a year (r) for t years is therefore given by:
Continuous Compounding Formula :
Pert
Compounding formula:
At=P×(1+i)t
Discounting Formula=
(Present Value)
(i.e. PV of redemption value for bonds)
The discounting process essentially involves reversing the growth process involving compound interest rates.
i.e. What is the present value of £133.10 received after 3 years at a 10 percent interest rate ?
PV = At(1+ i)−t
Present value=
Referred to as discounting
What value, P, must be invested now in order to obtain a particular future sum, At (i.e. the value of tomorrow’s money today)
Payback Period (PBP) =
The payback period is the time needed for the nominal cash generated by a project (sum of the yearly cash flows) to be equal to the cash injection needed.
In other words, payback occurs during the year in which positive cumulative cash flows is first achieved.
Average Rate of Return (ARR) =
ARR is the average percentage return per time period (normally one year) on the initial capital outlay over the expected life of the project:
Net Present Value (NPV) =
The total of the PVs of the cash inflows (revenues) less the initial capital outlay is the Net Present Value (NPV)
NPV > 0 ⇒ Value created
• Project with largest NPV according to the assumed rate of interest is the most profitable:
A project has the following cash flow (£)
Now -1200 Yr1=700 Yr2=800
What is the NPV if the discount rate is:
(a) 5%
.The higher the rate of discount we use in calculating the NPV…
The lower the value of NPV, i.e. there is an inverse relationship
If projects have different degrees of ‘risk’, then a higher rate of discount should often be applied to the riskier project(s)
Internal Rate of Return (IRR) =
The discount rate (i) which makes the net present value of a project equal to zero (i.e. it is the effective interest rate you are earning on the money you invest in the project)
Formule équation second degré (quadratic)=
Δ=b2-4ac
Si Δ=0, x= -b/(2a)
Si Δ>0, 2 solutions:
(-b± √Δ)/2a
Linear Interpolation Method (to be used to calculate IRR if project has more than 2 periods)
Calculate the NPV with two different discount rates, such that one (R1) gives a positive and the other (R2) a negative NPV
- Calculate IRR by using the formula:
Depreciation =
Just as some investments grow at a simple or compound rate due to interest rates on an initial amount, other investments might decline as a result of depreciation:
book value of capital equipment and other assets reduce through simple ‘wear and tear’
Straight line depreciation=
Reduces the value of capital by the same absolute amount each year
Annual depreciation =
(initial value - scrap value)/estimated life
Reducing Balance Depreciation: =
Most capital items do not depreciate in a linear fashion:
Sum (Sn) of a finite geometric progression:
Sinking Fund =
Regular savings arrangement with a financial institution.
An amount P is saved regularly for a specified period at a fixed rate.
The accumulated capital over the period is then computed as just described
Present Value Annuities Formula =
(i.e: mortgages, annuities, coupons from bonds)
Future Value Annuities formula =
Repayment Mortgage
- When a mortgage is taken out on a property it can be repaid by a series of regular payments.
- The mortgage is thus the present value of all future instalments
Interest Only Mortgage
- Only the interest is paid over the mortgage period.
- The capital (loan) is paid in a lump sum at the end of the mortgage period and is normally accumulated by a regular savings arrangement.
- The monthly cost of the mortgage is thus the monthly interest plus the amount to be accumulated (in a sinking fund):
Monthly Cost = Interest + Savings Amount
Annual Percentage Rate
(i.e. 1 year loan at 2% per month)
APR = [1(1 + i)t - 1] * 100
The equation of a straight line is
y = ax + b
Where:
b is the intercept
a is the slope or gradient
Where we have the maximum at x1 =
the value of the first derivative is zero, and the value of the second derivative (at x1) is negative.