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Let's first understand what a discount calculation involves. A discount is a reduction applied to the original price of an item. It is usually given as a percentage. In this case, the discount on the computer is 20%. To find the discount amount, you multiply the original price by the percentage of the discount (expressed as a decimal).
For example, a 20% discount means you calculate 20% of the original price. If the original price is expressed as \( p \) dollars, the discount is calculated as follows:

• Convert the percentage to a decimal: 20% becomes 0.20.
• Multiply the original price \( p \) by 0.20.

This gives us: \[ \text{Discount Amount} = p \times 0.20 \].
This tells us how much money is subtracted from the original price due to the discount.

Understanding percentages is crucial for working with discounts. Percentages represent a fraction of 100. For instance, 20% means 20 out of 100 or 0.20 when converted to a decimal. Percentages simplify comparison and calculations of parts of a whole.
To convert a percentage into a decimal, divide by 100. For example, 20% becomes 0.20, and 50% becomes 0.50. Similarly, to convert a decimal back to a percentage, multiply by 100.
Knowing how to work with percentages helps in situations like calculating discounts, interest rates, and other financial metrics. It is a fundamental concept in mathematics and everyday life.

Multiplication is a basic arithmetic operation that combines groups of equal sizes. In the context of discount calculations, multiplication helps us find a percentage of a given number.
For instance, if you know the original price of a computer is \( p \) dollars, and you need to find 20% of \( p \), you multiply \( p \) by 0.20:

• Original Price = \( p \)
• Discount Percentage = 20% or 0.20 (as a decimal)
• Discount Amount = \[ p \times 0.20 \]

Multiplying these values gives the amount that will be deducted.
This forms the basis for finding the sale price: subtract the discount amount from the original price.
In summary, \[ \text{Sale Price} = p - (p \times 0.20) = p \times 0.80 \].Multiplication simplifies and clarifies many financial calculations, making it easier to handle percentages and discounts.