Scaling Up: Multiplication
Multiplication is the operation of repeated addition, used to find the total when combining equal groups. It covers multiplying whole numbers, decimals, and fractions, building fluency with facts, multi-digit algorithms, and mental math strategies that are essential for more advanced mathematics and real-world problem solving.
Components of Multiplication
This section breaks down the core aspects of performing multiplication across different number types:
- Whole Numbers: Multiplying integers using the standard algorithm, focusing on place value and partial products.
- Decimals: Multiplying numbers with decimal points, then placing the decimal in the product correctly.
- Fractions: Multiplying numerators together and denominators together, simplifying when possible.
- Applications of Multiplication: Practical uses such as calculating areas, total costs, and scaling recipes.
Examples of Multiplication
Whole Numbers Examples
- Multiplying 12 Γ 7: Break it into 10 Γ 7 = 70 and 2 Γ 7 = 14, then add 70 + 14 to get 84.
- Multiplying 23 Γ 15: Calculate 23 Γ 5 = 115 and 23 Γ 10 = 230, then add 115 + 230 to get 345.
- A teacher orders 8 packs of 24 pencils, multiplying 8 Γ 24 to find a total of 192 pencils.
Decimals Examples
- Multiplying 2.5 Γ 4: Multiply 25 Γ 4 = 100, then place the decimal one position from the right, giving 10.0.
- Multiplying 1.2 Γ 3.5: Multiply 12 Γ 35 = 420, then place the decimal two positions from the right, giving 4.20.
- A fabric store sells ribbon at 3.75 dollars per meter, and a customer buys 2 meters, multiplying 3.75 Γ 2 to get 7.50 dollars.
Fractions Examples
- Multiplying 2/3 Γ 3/4: Multiply numerators 2 Γ 3 = 6, denominators 3 Γ 4 = 12, giving 6/12, which simplifies to 1/2.
- Multiplying 5 Γ 1/3: Rewrite 5 as 5/1, then multiply 5 Γ 1 = 5 and 1 Γ 3 = 3, giving 5/3 or 1 2/3.
- A recipe calls for 3/4 cup of sugar but you want to make half the recipe, multiplying 3/4 Γ 1/2 to get 3/8 cup.
Applications Examples
- A rectangular garden is 6 meters by 4.5 meters, multiplying 6 Γ 4.5 to find an area of 27 square meters.
- A store sells 15 shirts at 12 dollars each, multiplying 15 Γ 12 to find total revenue of 180 dollars.
- A car travels at 55 miles per hour for 3 hours, multiplying 55 Γ 3 to calculate a distance of 165 miles.