1. Mental Math
1) Thanh's weekly gross wages are $450.00. Her deductions total 15% of
her wages. What is her take home pay?
2) What is 45% of 400?
3) Add $432.88 + $43.55 + $87.55 =
4) Find 7669 ­ 1442=
5) What is 15% of 250?
6) Brandon works 12 hours a week at $10.50/hour. If his taxes are $16.38,
CPP is $5.04 and EI is $3.22, what is his net pay?
7) How many hours is 195 minutes?
8) 23 x 18 =
9) What is10% of 45?
10) Fence boards are $4.25 each. How much does a dozen boards cost?
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2. Simple Interest
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3. Paying Interest Charges and Earning Interest Income
Financial institutions borrow and lend money. When you
deposit money in a financial institution, you are lending the
financial institution money for a period of time. The financial
institution pays interest to you for borrowing your money.
In turn, the financial institution lends your money to
individuals who need it. These individuals are charged interest for
the money they borrow.
The interest rate investors receive when they deposit their
money with a financial institution is less than the interest rate they
must pay when they borrow from the same financial. In this way,
the financial institution makes a profit on these transactions.
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4. 4

5. The Simple Interest Formula
In summary, when you invest in a financial institution, the institution
pays you interest for using your money. When you borrow money from
a financial institution, you pay interest to them.
I = Prt,
I = interest earned or charged
P = principal, or amount invested or borrowed
r = annual (yearly) rate of interest expressed as a decimal
t = length of time in years
For simple interest the amount of the interest is not added to the
principle.
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6. Example 1
Olive Branch invests $1500 in a financial institution that offers
her a simple interest rate of 4% per annum (per year).
Calculate the interest (rounded to the nearest cent) Olive will
earn at the end of:
1. 3 years
2. 7 months
3. 100 days
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7. To calculate the rate, divide the interest by the product of the
principal and the time.
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8. To calculate the time, divide the interest by the product of the
principal and the rate.
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9. Example 2
Treya Pine invested a certain sum of money in a financial
institution and earned $200 interest after four years. If the
annual interest rate was 5%, what amount did Treya invest?
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10. Example 3
Brooke Poole has $2400 to invest in a financial institution.
Calculate the annual rate of interest if she plans to earn $300 on
her investment at the end of two years.
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11. Example 4
Wade Lake deposits $5000 in an account earning interest
at a rate of 4% per year. Calculate the number of days
Wade must keep the money in his account to earn interest
of $360.
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12. Assignment
Read page 28­31
Page 32 questions 1, 2, 3, 5, 7
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