Calculating Percentages

Study Notes

Calculating Percentages

Percentages are a common way of expressing the proportion of one quantity to another. They can be used to compare different quantities, to measure change over time, or to describe rates and ratios. Here's how you calculate percentages:

Finding Percentage of a Number

To find the percentage of a number, divide the part into the whole and multiply by 100:

(part / whole) * 100 = percentage

For example, if you have 9 apples out of 15 total fruits, the percentage is:

(9 / 15) * 100 = 60%

The calculation shows that 60% of the total fruits are apples.

Converting Decimals to Percentages

You can convert decimals to percentages by moving any decimal point to the right, and then adding a percent sign (%) at the end. For example, 0.8 becomes 80%, and 0.06 becomes 6%.

Solving Straight Percentages Problems

Straight percentages problems involve finding the unknown value when you know what percentage it represents of a known value:

Unknown Value x = Known Value * Percentage / 100

If you want to find out how many years a company has been operating, and it currently employs 75% of its previous workforce, you can set up the equation like this:

x = 100 * 75 / 100
x = 75

This means there are 75 years of operating history.

Finding Percentage Increases and Decreases

To find the percentage increase or decrease, first find the absolute increase or decrease, and then divide by the original value and multiply by 100:

Percentage Increase/Decrease = (New Value - Old Value) / Old Value * 100

For example, if a city's population increases from 500,000 to 600,000, the percentage increase is:

(600,000 - 500,000) / 500,000 * 100 = 20%

This means the population has increased by 20% compared to the original size.

Calculating percentages is a fundamental skill in mathematics and can be applied to various fields. With practice, you'll be able to solve various percentage problems easily.

Description

Learn how to calculate percentages, find percentage of a number, convert decimals to percentages, solve straight percentages problems, and find percentage increases and decreases. Master this fundamental skill in mathematics and apply it to various fields.