Grade 6 → Ratio and Proportion ↓
Percentages
In everyday life, we often encounter percentages. Whether you're looking at shopping discounts, reading statistics in the news, or calculating your grades in school, percentages are everywhere. In this guide, we'll explore what percentages mean, how they relate to ratios and proportions, and how you can easily calculate them. By the end of this guide, you'll have a good understanding of percentages and be able to solve a variety of problems involving them.
What is the percentage?
A percentage is a way of expressing a number as a fraction of 100. It is represented by the "%" sign. For example, 50% means 50 out of 100, or simply 50/100. The word "percent" comes from the Latin percentum, meaning "from a hundred". This makes it a very useful tool for comparing different quantities, especially when working with hundred units.
Converting fractions to percentages
To convert a fraction to a percentage, you need to multiply the fraction by 100, and then add the percent sign "%". Let's look at an example:
Fraction: 3/4
To convert 3/4 to a percentage:
Percentage = (3/4) * 100 = 75%
This means that 3/4 is equal to 75%.
Converting decimals to percentages
Similarly, converting a decimal to a percentage involves multiplying the decimal value by 100 and then adding the "%" sign. Let's take an example of a decimal:
Decimal: 0.85
To convert 0.85 to a percentage:
Percentage = 0.85 * 100 = 85%
So 0.85 as a percentage is 85%.
Visual representation of percentages
Visual aids can help make percentages easier to understand. Consider a pie chart that shows a full circle divided into 100 equal parts. Each part represents 1% of the whole. For example, if we shade 30 of those parts, it represents 30% of the whole circle.
Understanding ratio and proportion with percentages
Ratios compare two values, showing how much there is of one thing compared to another. For example, if you say the ratio of cats to dogs is 3:4, that means that for every 3 cats, there are 4 dogs. Percentages can also represent this ratio. To find the percentage that equals the part of the whole represented by the ratio, write the ratio as a fraction, and then convert the fraction to a percent.
Example:
Let the ratio of apples to total fruits be 3:8.
Fraction of apples = 3/8 Percentage of apples = (3/8) * 100 = 37.5%
This shows that the share of apples in total fruits is 37.5%.
Ratio and percentage
Ratios are statements that say that two ratios or fractions are equal. For example, if we have the ratio 1/2 = x/100, this means that 1 out of 2 is equal to x out of 100, or x percent. Solving for x gives us the equivalent percentage.
1/2 = x/100 => x = (1/2) * 100 => x = 50
So 1/2 = 50%.
Uses of percentages in real life
Percentages are often used to calculate discounts. If a $60 sweater is on sale for 25% off, you can determine the discount amount by calculating 25% of 60, then subtracting it from the original price.
Discount = 25% of $60 = (25/100) * $60 = $15 Selling price = $60 - $15 = $45
Thus, the price of the sweater after the discount will be $45.
Example problems
Let us work on some more examples to further strengthen our understanding.
Problem 1: Percentage of a number
Find 20% of 150.
20% of 150 = (20/100) * 150 = 30
So, 20% of 150 = 30.
Problem 2: Calculating percentages in reverse
If a student scores 84 marks out of a possible 120, what is his percentage mark?
Percentage = (84/120) * 100 = 70%
The student scored 70% marks.
Problem 3: Comparing percentages
Which is greater: 40% of 200 or 50% of 150?
40% of 200 = (40/100) * 200 = 80 50% of 150 = (50/100) * 150 = 75
40% (80) of 200 is greater than 50% (75) of 150.
Conclusion
Understanding percentages and their relationship to ratios and proportions is an essential skill that helps in a variety of everyday calculations. From calculating discounts to understanding statistics and comparing quantities, percentages make it easier to visualize and understand numerical relationships. We hope this guide has given you a clear understanding of percentages and equipped you with the skills to confidently handle complex percentage-based problems.