How to Determine Percentage of Two Numbers

April 24, 2025 3 min read

Understanding percentages is a fundamental skill, useful in everyday situations ranging from calculating discounts to analyzing statistical data. This article will break down the process of how to determine percentage of two numbers, ensuring you grasp the core concepts and can apply them confidently.

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Understanding the Basics of Percentages

A percentage represents a portion of a whole, where the whole is considered to be 100%. The term "percent" literally means "per hundred." So, when you say 25%, you mean 25 out of 100. Understanding this basic principle is essential for tackling more complex percentage problems.

The Core Question: "What Percentage Is X of Y?"

The most common scenario is figuring out what percentage one number (X) represents of another number (Y). For instance, you might want to know what percentage 30 is of 150. The formula to solve this is:

Percentage = (X / Y) * 100

In our example, it would be:

Percentage = (30 / 150) * 100 = 20%

This means 30 is 20% of 150.

Step-by-Step Guide: Determining Percentage

  1. Identify the Two Numbers: Know which number is the part (X) and which is the whole (Y).
  2. Apply the Formula: Divide the part (X) by the whole (Y), then multiply by 100.
  3. Interpret the Result: The answer is the percentage that X represents of Y.

For instance, if you want to find what percentage 45 is of 225:

Percentage = (45 / 225) * 100 = 20%

Therefore, 45 is 20% of 225.

Real-World Applications

Knowing how to determine percentage of two numbers has countless real-world applications:

  • Calculating Discounts: If an item originally costs $80 and is on sale for $60, what percentage discount are you receiving? Calculate the discount
  • Analyzing Test Scores: If you scored 75 out of 90 on a test, what was your percentage score?
  • Tracking Progress: If you've saved $500 towards a $2000 goal, what percentage of your goal have you achieved?

Percentage Increase and Decrease

Sometimes, you need to calculate the percentage increase or decrease between two values. The formulas are slightly different:

  • Percentage Increase: [(New Value - Original Value) / Original Value] * 100
  • Percentage Decrease: [(Original Value - New Value) / Original Value] * 100

For example, if a company's revenue increased from $100,000 to $120,000, the percentage increase is:

Percentage Increase = [($120,000 - $100,000) / $100,000] * 100 = 20%

If the price of a product decreased from $50 to $40, the percentage decrease is:

Percentage Decrease = [($50 - $40) / $50] * 100 = 20%

Common Mistakes and How to Avoid Them

While the formulas are simple, mistakes can occur. Here are some common errors and tips to avoid them:

  • Incorrectly Identifying the Part and Whole: Always double-check which number is the part and which is the whole.
  • Forgetting to Multiply by 100: Remember to multiply the result of the division by 100 to express it as a percentage.
  • Misinterpreting Increase/Decrease: Ensure you use the correct formula for increase or decrease, depending on the scenario.

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