Chapter 2: Financial Maths Flashcards
What is compounding?
Compounding is calculating the interest on the principal sum and the existing interest.
What is discounting?
Discounting is the reverse of compounding; it is working out what an amount of money to be received in the future is worth in today’s terms.
What is an annuity?
A series of payments to be received over a fixed time. A real-world application is with pensions where on retirement the value of your pension fund is used to purchase an annuity.
What is present value?
Present value is what something is worth in today’s terms.
What is ‘interest’ also known as?
‘cost of capital’ or the ‘time value of money’
Define ‘compound interest’.
When interest is permitted to accumulate on top of the principal borrowed in order to earn interest itself.
Define ‘simple interest’.
When interest is withdrawn at the end of each period and not aggregated to the principal.
How is simple interest calculated?
Simple interest is calculated on the original principal amount only.
It assumes at the end of each period that earned interest is not summed together with the principal.
For example, a £1,000 deposit placed at 5% per annum for three years will earn £150 of interest i.e. 3 multiplied by £50 per annum.
What is the formula used to calculate the future value (FV) of a lump sum invested at a rate of interest (r) over a given number of years (n) on a simple interest basis?
FV = original principal amount x [1 + (r x n)].
Using the numbers in the above example: TV = £1,000 x [1 + (0.05 x 3)] = £1,150
FV = £1,000 x 1.15 = £1,150r
What assumptions are made when calculating compound interest?
Compound interest assumes that interest earned for one period is ‘rolled-over’ into subsequent periods. The interest rate applies to the principal plus accrued interest. When applying compound interest, it is assumed that interest earned is re-invested i.e. earning interest on interest. Interest payments will therefore increase exponentially over time.
For example, a three-year deposit of £1,000 at 5% pa would accrue to £1,050 at the start of the second year. This amount earns interest of £52.5 (£1,050 x 0.05) which itself is rolled over into the third year.
What formula is used to calculate the future value (FV) of a lump sum receiving compound interest?
FV = PV(1 +r)n
Where:
- FV is the future value of the deposit (how much capital and compounded interest there will be in total).
- PV is the amount of money to be deposited, or the present value of the deposit.
- n is the number of periods the deposit is to run for (the usual period is a year).
- r is the rate of interest on the deposit per period.
What is the reinvestment return?
The additional income generated through reinvesting income.
What is the reinvestment return formula?
Reinvestment Return = Compound Return - Simple Return
Compound Return = FV - PV
FV = PV(1+r)n therefore compound return = PV(1+r)n-PV
simple return = PV × r × n
N.B. the formula for the sumple return is different to the formula for the future value it excludes the 1, this is because we just want to know the income that is generated.
An investor receives a dividend of £5,000 from their investment portfolio. They decide to reinvest this in a fixed rate deposit account for 10 years at 3.5%. Calculate the investor’s reinvestment return.
Income from shares = £5,000 x 0.035 x 10 years = £1,750.00
Compound return = £5,000 x 1.03510 − £5000 = £2,052.99
Reinvestment return = £2,052.99 – £1,750 = £302.99
This increases the return by approximately 1.6% per year. Now imagine the investor doing this with every dividend they receive.
How is the FV calculated for non-annual compounding periods? For example, if If the frequency of compounding increased to quarterly intervals for a 3 year investment with a 5% return, what would the FV be?
We would need to increase the number of periods ‘n’ by 4 (from 3 years to 12 quarter), but reduce the rate of interest by 4 (from 5% p.a. to 1.25%) per quarter in return. Using the figures above, but with quarterly compounding, we would get:
1000 x 1.012512 = 1160.75
This is a higher value than compounding over annual intervals. Note, reinvestment return has increased to £10.75
What is continuous compounding?
- Continuous compounding is the mathematical limit that compound interest can reach if it’s calculated and reinvested into an account’s balance over a theoretically infinite number of periods.
- Instead of calculating interest on a finite number of periods, such as yearly or monthly, continuous compounding calculates interest assuming constant compounding over an infinite number of periods.
- Compounded continuously means that interest compounds every moment, at even the smallest quantifiable period of time. Therefore, compounded continuously occurs more frequently than daily.
What Is the Difference Between Discrete and Continuous Compounding?
Discrete compounding applies interest at specific times, such as daily, monthly, quarterly, or annually. Discrete compounding explicitly defines the time when interest will be applied. Continuous compounding applies interest continuously, at every moment in time.
What is the rate of compounding for continour compounding?
millisecond by millisecond
What is the formula used to calculate the continuous compound interest rate?
FV = PV x e(r x n)
Calculate the continuous compound interest rate for a £1000 investment with a return of 5% pa over 3 years.
PV = £1,000 r = 5% pa n = 3 e = natural exponent
FV = PV x e(r x n)
= £1,000 x e(0.05 x 3)
= £1,161.83
Again, reinvestment return has increased further to £161.83
What is discounting?
Discounting is the exact opposite of compounding. Discounting is concerned with determining how much to invest today, given a rate of interest (the ‘discount rate’) and frequency of payment, in order to achieve a required terminal value in the future.
What are the methods used to calculate the present value of future cash flows known as?
Discounted cash flow (DCF) techniques.
How is the present value of a single lump sum due to be received on a future date at a given level of interest calculated?
By re-arranging the compounding equation to make PV (present value) the subject of the formula.
What is the formula for calculating the present value?
PV = FV/(1+r)n
What is the formula for calculating the present value?
PV = FV/(1+r)n
Where:
- FV is the amount of money to be received in the future.
- PV is the present value of the amount (how much FV is worth now).
- n is the number of periods until the amount is received (the usual period is a year)
- r is the rate of interest on the deposit per period