What Percentage Is X of Y - Complete Guide

Understanding the Concept

When you ask "What percentage is X of Y?", you're trying to find out what proportion or fraction X represents of the total Y. This is one of the most common percentage calculations in everyday life.

For example: If you scored 42 out of 50 on a test, what percentage did you get? Or if 15 out of 60 people attended a meeting, what percentage showed up?

The Formula

To find what percentage X is of Y, use this simple formula:

Percentage = (X ÷ Y) × 100

Where:
• X = the part (the smaller number)
• Y = the whole (the total or larger number)

Step-by-Step Examples

Example 1: Test Score

Question: You scored 42 out of 50 on a test. What percentage is that?

Solution:
Step 1: Identify X and Y: X = 42, Y = 50
Step 2: Divide X by Y: 42 ÷ 50 = 0.84
Step 3: Multiply by 100: 0.84 × 100 = 84%
Answer: You scored 84%

Example 2: Meeting Attendance

Question: 15 out of 60 people attended a meeting. What percentage showed up?

Solution:
Step 1: Identify X and Y: X = 15, Y = 60
Step 2: Divide X by Y: 15 ÷ 60 = 0.25
Step 3: Multiply by 100: 0.25 × 100 = 25%
Answer: 25% of people attended

Example 3: Sales Target

Question: A salesperson sold R45,000 worth of products. Their target was R60,000. What percentage of the target did they achieve?

Solution:
Step 1: Identify X and Y: X = R45,000, Y = R60,000
Step 2: Divide X by Y: 45,000 ÷ 60,000 = 0.75
Step 3: Multiply by 100: 0.75 × 100 = 75%
Answer: They achieved 75% of their target

Example 4: Budget Spending

Question: You've spent R2,400 of your R3,000 monthly budget. What percentage have you used?

Solution:
Step 1: Identify X and Y: X = R2,400, Y = R3,000
Step 2: Divide X by Y: 2,400 ÷ 3,000 = 0.80
Step 3: Multiply by 100: 0.80 × 100 = 80%
Answer: You've used 80% of your budget

Example 5: Survey Results

Question: In a survey of 250 people, 175 said "yes". What percentage is that?

Solution:
Step 1: Identify X and Y: X = 175, Y = 250
Step 2: Divide X by Y: 175 ÷ 250 = 0.70
Step 3: Multiply by 100: 0.70 × 100 = 70%
Answer: 70% said "yes"

Example 6: Completion Progress

Question: You've completed 8 chapters of a 12-chapter book. What percentage have you finished?

Solution:
Step 1: Identify X and Y: X = 8, Y = 12
Step 2: Divide X by Y: 8 ÷ 12 = 0.6667
Step 3: Multiply by 100: 0.6667 × 100 = 66.67%
Answer: You've completed approximately 66.67% of the book

When X is Greater Than Y

Sometimes X can be larger than Y, resulting in a percentage over 100%. This is perfectly valid.

Example 7: Exceeding Target

Question: A salesperson sold R75,000 worth of products with a target of R60,000. What percentage of the target did they achieve?

Solution:
75,000 ÷ 60,000 × 100 = 125%
Answer: They achieved 125% of their target (25% over target)

Common Applications

Education

• Converting test scores to percentages
• Calculating grade point averages
• Measuring assignment completion rates
• Tracking attendance percentages

Business & Finance

• Measuring sales performance against targets
• Calculating market share
• Analyzing profit margins
• Determining budget utilization

Health & Fitness

• Tracking workout completion
• Measuring daily calorie intake vs. goals
• Calculating body fat percentage
• Monitoring medication adherence

Project Management

• Measuring project completion
• Tracking milestone achievements
• Calculating resource utilization
• Monitoring task completion rates

Personal Life

• Savings progress toward goals
• Book or course completion
• Time spent on activities
• Task list completion

Quick Mental Math Tricks

When Y = 100: X is already the percentage (e.g., 25 out of 100 = 25%)

When Y = 10: Multiply X by 10 (e.g., 7 out of 10 = 70%)

When Y = 50: Multiply X by 2 (e.g., 30 out of 50 = 60%)

When Y = 25: Multiply X by 4 (e.g., 20 out of 25 = 80%)

When Y = 4: Multiply X by 25 (e.g., 3 out of 4 = 75%)

Common Mistakes to Avoid

Mistake 1: Dividing in Wrong Order

Wrong: Y ÷ X × 100
Correct: X ÷ Y × 100
Always divide the part by the whole, not the other way around.

Mistake 2: Forgetting to Multiply by 100

If you get 0.75 as your answer and stop there, you haven't converted to a percentage yet. Always multiply by 100 to get the percentage (0.75 becomes 75%).

Mistake 3: Confusing Part and Whole

Make sure you identify which number is the part (X) and which is the whole (Y). The whole is usually the total, maximum, or target value.

Related Calculations

Finding X When You Know the Percentage

Question: What is 35% of 200?
Formula: X = (Percentage ÷ 100) × Y
Solution: X = (35 ÷ 100) × 200 = 70

Finding Y When You Know the Percentage

Question: 60 is 40% of what number?
Formula: Y = X ÷ (Percentage ÷ 100)
Solution: Y = 60 ÷ 0.40 = 150

Practice Problems

Problem 1: What percentage is 18 of 24?
Answer: 75%

Problem 2: What percentage is 65 of 200?
Answer: 32.5%

Problem 3: What percentage is 7 of 8?
Answer: 87.5%

Problem 4: What percentage is 150 of 120?
Answer: 125%

Problem 5: What percentage is 33 of 150?
Answer: 22%

Real-World Scenarios

Scenario 1: Restaurant Tip

Your meal costs R180 and you want to leave a R27 tip. What percentage tip is that?
27 ÷ 180 × 100 = 15% tip

Scenario 2: Discount Shopping

An item originally costs R400 and you're paying R300. What percentage of the original price are you paying?
300 ÷ 400 × 100 = 75% (which means you got a 25% discount)

Scenario 3: Work Hours

You worked 35 hours in a week where your target was 40 hours. What percentage of your target did you work?
35 ÷ 40 × 100 = 87.5%

Use Our Calculator

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What Percentage Is X of Y?