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Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof [email protected] http://people.virginia.edu/ ~ans5k/ Math 1140 Financial Mathematics

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Page 1: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Lecture 12Compound Interest

Ana Nora Evans 403 [email protected]://people.virginia.edu/~ans5k/

Math 1140 Financial Mathematics

Page 2: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

2Math 1140 - Financial Mathematics

A) I finished homework 5.B) I didn’t start homework 5.C) I got stuck in a problem in homework 5.D) Do we have a homework!?

If you answered C you should come to the office hours.

Page 3: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

3Math 1140 - Financial Mathematics

Office Hours

Monday 11:00-12:30Tuesday 3:30-5:00 Friday 2:30-3:30 In Ker 403.

Page 4: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

4Math 1140 - Financial Mathematics

Review Session

It is not required.It will be useful for students that joined the class late and missed the first few classes.It offers the chance to clarify some concepts from the previous classes.

Page 5: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 5

I am sorry for Sunday. Is Wednesday 7pm working for you?

A) It works and I plan to come.

B) I can come to office hours instead.

C) I would like to come but I have other commitments.

D) I don’t need extra help.

If you answered C please email me to make an appointment or come prepared to ask questions on Friday and Monday.

Review Session

Page 6: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

6Math 1140 - Financial Mathematics

Questions

About last classAbout homework

Page 7: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

7Math 1140 - Financial Mathematics

Sample exam 1 postedPractice exercises posted (we will work on them in class on Friday, Sep 23, and Monday, Sep 26).Exam 1 covers sections 1.2 trough 1.9 sections 2.1 trough 2.5 sections 3.1 and 3.2

Page 8: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

8Math 1140 - Financial Mathematics

Plan for this week

Monday(today) – sections 3.4 and 3.5Wednesday – sections 3.6 and 3.7Friday and Monday(exam review, work in groups on practice problems, class in Rice Hall first floor)

Page 9: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

9Math 1140 - Financial Mathematics

Last time

Started compound interest.Compound amount formulaPresent value at compound interest

Sections 3.1 and 3.2

Page 10: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

10Math 1140 - Financial Mathematics

Today

Annual effective rateAnnual effective rate of compound discountCompound rate formula

Sections 3.4 and 3.5

Page 11: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 11

m is the number of conversion periods per year.

i(m) is the nominal interest rate.

Interest rate per conversion period i = i(m)/m

Nominal Interest Rate and Interest Rate

Page 12: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 12

Compound amount formula is S = P(1+i)n

where

n is the total number of conversion periods

P is the principal

S is the amount

i is the interest rate per conversion period

Present value formula at compound interest is

P = S(1+i)-n

Page 13: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

13Math 1140 - Financial Mathematics

Obsetvation

n, the total number of conversion periods is a natural number.For any fractions of a conversion period, use simple interest formula.E.g., after calculations you end up with 3.5 conversion periods then the amount is S = (P(1+i)3)(1 + 0.5 x i)

Page 14: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

14Math 1140 - Financial Mathematics

Questions?

Page 15: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 15

Suppose that a savings account pays 3% interest per quarter compounded quarterly. If $2,500 is deposited, how much is in the account 5 years later?

A) 2,500(1+0.03/4)-5

B) 2,500(1+0.03)-20

C) 2,500(1+0.03/4)5

D) 2,500(1+0.03)20

E) I don’t know

Pledged Question

Page 16: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 16

Suppose that a savings account pays 3% interest per quarter compounded quarterly. If $2,500 is deposited, how much is in the account 5 years later?

Answer

The interest rate is given as interest rate per conversion period, thus i = 3%. Since there are 4 conversion periods per year and the term is 5 years, then n = 20. The principal is P=$2,500. The correct answer is 2,500(1+0.03)20

Page 17: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

17Math 1140 - Financial Mathematics

Google Group

I created a google group for this class FinMathFall2011. You must join the group to receive class emails. The 13 students did not join are doing it at their own risk.One of the messages on the group list tells you how to subscribe for updates of the class website.

Page 18: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

18Math 1140 - Financial Mathematics

Emails

To receive my emails you must whitelist my email addresses:[email protected]@[email protected]

Page 19: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

19Math 1140 - Financial Mathematics

Warning

From now on you are responsible for any emails sent to your UVa email address and to the FinMathFall2011 google group.

Page 20: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

20Math 1140 - Financial Mathematics

Annual Effective Rate

Given a nominal interest rate i(m), the annual effective rate is the interest rate i such that if the same principal P is deposited in two accounts: one with nominal interest rate i(m) and one with yearly interest rate i, compounded yearly; at the end of one year the two accounts have the same balance.

Page 21: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 21

The compounded amount formula is S = P(1+i)n

The balance in an account with nominal interest rate i(m) after one year is:

S = P(1 + i(m)/m)m

The balance in an account with interest rate i per year, compounded yearly, after one year is

S = P(1 + i)1

To calculate i

P(1 + i) = P(1 + i(m)/m)m

i = (1 + i(m)/m)m - 1

Page 22: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

22Math 1140 - Financial Mathematics

Why does one calculate annual effective rate?

It allows us to compare different nominal interest rates.

You are considering two different savings accounts. The first pays 4.7% compounded monthly and the second one pays 4.63% compounded daily. Which one is the better deal?

Page 23: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 23

You are considering two different savings accounts. The first pays 4.7% compounded monthly and the second one pays 4.63% compounded daily. Which one is the better deal?

The annual effective rate formula is

1+i = (1 + i(m)/m)m

For the first account:

For the second account:

Page 24: Lecture 12 Compound Interest Ana Nora Evans 403 Kerchof AnaNEvans@virginia.edu ans5k/ Math 1140 Financial Mathematics

Math 1140 - Financial Mathematics 24

Wednesday

Homework 5 due

Read sections 3.4, 3.5,

3.6, 3.7

Friday and Monday

Exam 1 review

First Exam (max 15 points):

26 September 2011 at 7pm

in CLK 108

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