1203AFE Lecture Notes - Lecture 4: Promissory Note, Effective Interest Rate, Interest
Week 4 Money, Bank and Finance
Numeracy 2- Introduction to Financial Maths
Simple Interest
• Simple Interest is interest that is charged only on the principal or the amount of
money borrowed.
• Simple interest is calculated using the formula:
o I is the simple interest amount
o P is the principal or the amount borrowed or invested
o r is the (annual) rate of interest
o t is the time period of the loan or investment, which may be in whole
numbers (for a number of years) or stated as a fraction of 365 days for some
part of one year
Example
• Find the simple interest on a loan of $20,000 for three years at an annual rate of 12%
• Solving for P
o John knows that in 6 months he will have to pay tuition fees at college of
$365. He wants to deposit a sum of money now and use the interest on the
principal to pay the fees in 6 months time. He can earn an annual rate of 12%
on his money. How much should he invest now to earn the fees?
PV and FV
• The future value (FV) of a sum of money is the principal plus interest, or the amount
received in the future.
• The present value (PV) is the sum invested or borrowed today, or the principal. It is
also the future value discounted back to today using the applicable interest rate and
number of time periods.
• Time value of money - Clearly if someone offers
you $1,000 you would prefer to receive the money
now rather than in one years time.
Example- Time Value of Money
• For example, the present value of $1,000 to be
received in one years tie is alulated as (at
10%):
tI
Pr
=
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Example- Future Value
• FV formula is derived from the simple interest formula as for a single sum is defined
as:
• Loan for $40,000, annual simple interest rate is 12%, repaid in 9 months.
• What is the FV (i.e. how much is to be repaid including interest in 9 months?)
Example- Present Value
• The present value of a sum of money is its value today. We can rearrange the
formula for the future value of a single sum to:
• Amount invested at time zero (now) to give a
future value of $600 in 45 days at 7% interest?
Simple Discount
• For some securities a simple discount applies.
• The interest charge is based on the maturity value of the security and the borrower
receives less than the full amount borrowed.
• The discount (D) is calculated as the future value (FV) multiplied by the discount rate
(d) multiplied by the number of years (t).
• The present value, or price, then becomes
the future value less the discount.
Example
• A loan for $3000, 2 years, simple discount rate
of 9%.
• Calculate interest on the loan. →
• Interest = $540 and the proceeds of the loan
are therefore $3,000 less the discount of $540, which equals $2,460.
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Document Summary
Simple interest: simple interest is interest that is charged only on the principal or the amount of money borrowed, simple interest is calculated using the formula: Example: find the simple interest on a loan of ,000 for three years at an annual rate of 12, solving for p, john knows that in 6 months he will have to pay tuition fees at college of. He wants to deposit a sum of money now and use the interest on the principal to pay the fees in 6 months time. He can earn an annual rate of 12% on his money. Pv and fv: the future value (fv) of a sum of money is the principal plus interest, or the amount received in the future, the present value (pv) is the sum invested or borrowed today, or the principal. Example- time value of money: for example, the present value of ,000 to be received in one year(cid:859)s ti(cid:373)e is (cid:272)al(cid:272)ulated as (at.