Transcript Do Now 4/7/08

Do Now 4/23/10
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Take out HW from last night.
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Copy HW in your planner.
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Practice worksheet 7.6 odds
Text p. 365, #8-16 evens and #15
In your journal, answer the following question. A shoe
store in NJ has a sale on sneakers for 15% off. If the
original price is$75 what is the total cost of the sneakers
with tax?
A shoe store in NJ has a sale on sneakers for 15%
off. If the original price is$75 what is the total cost of
the sneakers with tax?
Sale price
Total Price
=
Original price
=
=
=
75
75
$63.75
=
Purchase Price
$63.75
$63.75
$68.21
–
–
–
+
+
Discount
(15% · 75)
11.25
+
Sales Tax
(63.75 x 7%)
4.46
Homework
Practice worksheet 7.6 odds
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1) $11.25
3) $273
5) $49.40
7) $30.60
9) $29.26
11) $86.51
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13) $83.64
15) $36.15
17) $19.38
19) $27.04
21) $57.40
Objective
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SWBAT calculate interest earned and account
balances
Section 7.7 “Simple and Compound Interest”
SIMPLE INTERESTIs the product of the principal, the annual interest
rate, and the time in years.
I  P r t
Principal – the amount borrowed, loaned, or in savings.
Annual interest rate – the percent of the principal you would
earn (or pay) as interest in ONE year.
Time in years – when time is less than a year, write time as a
fraction of the year.
Writing Time in Years…
I  P r t
Time in years – when time is less than a year, write time as a
fraction of the year.
Write the months as a fraction of a year.
3 months
7 months
3 1

12 4
7
12
10 months
10 5

12 6
Simple Interest
You have $1,000 in a savings account in a local
bank. The annual interest rate is 3%. How much
interest will the bank pay you in a month?
Principal = $1000
I  P r t
Interest rate = 3% or 0.03
1
I  1000  0.03 
12
Time = one month or 1/12
I  $2.50
Simple Interest
You borrowed $18,000 for a new car. The annual
interest rate is 12%. What is the interest you will
have to pay in two years to borrow this money?
Principal = $18,000
Interest rate = 12% or 0.12
Time = two years or 2
I  P r t
I  18000  0.12  2
I  $4320
Account Balance
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When an account earns interest it is added to the
money in the account. The BALANCE (A) of
an account that earns simple annual interest is
the sum of the principal (P) and the interest
(Prt).
A  P  Pr t
Balance
Finding an Interest Rate
Suppose you save $1400 in a savings account that
earns simple annual interest. After 9 months, the
balance in your account is $1421. Find the annual
interest rate.
Principal = $1400
A  P  Pr t
Balance = $1421
1421 1400 1400(3 / 4)r
Time = 9 months
21  1050 r
0.02  r
The interest
rate is 2%
This makes more “cents”…
COMPOUND INTEREST-
Is interest that is earned on BOTH the principal and any
interest that has been earned previously.
A  P(1  r )
t
Account balance– the amount of money in an account.
Principal – the amount borrowed, loaned, or in savings.
Annual interest rate – the percent of the principal you would
earn (or pay) as interest in ONE year.
Time in years – when time is less than a year, write time as a
fraction of the year.
This makes more “cents”…
You deposit $300 in the bank. This is your beginning balance. The
annual interest rate is 6%. Each year the simple interest is computed
and then added to your beginning balance. (this is compounded
interest). If this pattern continues, how much will you have in the
account at the end of 3 years?
Principal = $300
Interest rate = 6%
Time = 3 years
A  P(1  r )
t
A  300(1  0.06)3
A  $357 .30
After 3 years you will have $357.30
Compound Interest
You deposit $1,500 in a savings account in a local
bank. The annual interest rate is 2.4% compounded
annually. Find the balance after 6 years?
Principal = $1500
A  P(1  r )
Interest rate = 2.4% or 0.024
A  1500(1  0.024)6
Time = 6
A  $1729 .38
t
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Homework
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Text p. 365, #8-26 evens
Word Problem
You deposit $300 in the bank. This is your beginning balance. The
annual interest rate is 6%. Each year the simple interest is computed
and then added to your beginning balance. If this pattern continues,
how much will you have in the account at the end of 3 years?
After 3 years you will have $357.30
YEAR 1
YEAR 2
YEAR 3
Principal = $300
Principal = $318
Principal = $337.08
Interest rate = 6%
Interest rate = 6%
Interest rate = 6%
Time = one year
Time = one year
Time = one year
I  P r t
I  P r t
I  P r t
I  300  0.06 1
I  318  0.06 1
I  337 .08  0.06 1
I  $18
I  $19 .08
I  $20 .22