Money Knowledge-Based Study

Study notes

1. What Is Money?

   Money is a standard unit of measurement used to determine the value of goods and services, as well as to trade and pay for them.

   In standard decimal currency systems, money is divided into two primary units:

   • Dollars (or main units): Represented by the symbol $.
   • Cents (or fractional units): Represented by the symbol ¢, where 100 cents make up 1 whole dollar.

   Coins represent smaller fractional amounts such as 1¢ (penny), 5¢ (nickel), 10¢ (dime), and 25¢ (quarter), whereas banknotes typically represent larger values such as $1,$5, $10,$20, $50, and$100.

   Decimal Notation for Money

   Because 100 cents equal 1 dollar, money is written using two decimal places to show parts of a dollar:

   100¢ = $1.00

   The digits before the decimal point represent whole dollars, while the two digits following the decimal point represent cents.

   Examples of Conversion:

   • To convert cents to dollars, divide by 100: 345¢ = $3.45
   • To convert dollars to cents, multiply by 100: $6.20 = 620¢
   • Values with single-digit cents require a leading zero in the tenths place: 5¢ = $0.05

   Operations with Money

   When adding or subtracting amounts of money, align the decimal points vertically to ensure dollars align with dollars and cents align with cents.

   Addition (Finding Total Cost):

   Suppose you purchase an item for $4.35 and another item for$2.80:

   • Align the decimals: $4.35 +$2.80
   • Add the cents: 35¢ + 80¢ = 115¢ ($1.15)
   • Add the dollars: $4 +$2 + $1 (regrouped) =$7
   • Total = $7.15

   Subtraction (Calculating Change):

   Change is the amount of money returned to a buyer when they pay more than the total cost.

   Change = Amount Paid - Total Cost

   For example, paying with a $10.00 bill for an item costing$7.15:

   • $10.00 -$7.15 = $2.85
   • The buyer receives $2.85 in change.

   Practical Applications

   Real-world financial questions often combine multiple operations, such as purchasing multiple identical items or calculating total budget availability.

   Example Problem:

   A notebook costs $3.50 and a pen costs$1.25. If a student buys 2 notebooks and 3 pens and pays with a $20.00 note, how much change should they receive?

   1. Calculate cost of notebooks: 2 × $3.50 =$7.00
   2. Calculate cost of pens: 3 × $1.25 =$3.75
   3. Find total expenditure: $7.00 +$3.75 = $10.75
   4. Subtract from the total paid: $20.00 -$10.75 = $9.25

   The total change received is $9.25.