Calculating how much something goes up or down in percentage can seem tricky at first. But don’t worry! Once you understand it, it's pretty simple. I remember when I was in Year 8, trying to figure it out too. Let's break it down together, step-by-step.

What You Need to Know

Before we start, let’s understand what we mean by percentage increase and decrease.

• Percentage Increase: This happens when a value goes up. For example, if a book costs $10 and then it goes up to$12, that’s an increase.

• Percentage Decrease: This is when a value goes down. So, if that same book's price drops from $10 to$8, that’s a decrease.

How to Calculate Percentage Increase

1. Find the Original Value: This is your starting point. Let’s use $10.

2. Get the New Value: This is the price after the increase. Here, it’s $12.

3. Calculate the Difference: Subtract the original value from the new value.

   • So, $\text{Difference} = 12 - 10 = 2$

4. Divide the Difference by the Original Value: This helps you see how much the increase is compared to where you started.

   • In our case: $\text{Relative Increase} = \frac{2}{10} = 0.2$

5. Convert to Percentage: To change that into a percentage, multiply by 100.

   • So: $\text{Percentage Increase} = 0.2 \times 100 = 20\%$

How to Calculate Percentage Decrease

Calculating a percentage decrease is almost the same, with just a few changes.

1. Find the Original Value: We’ll still use $10.

2. Identify the New Value: This is the lower amount after the decrease. Let’s say it’s $8.

3. Calculate the Difference: Subtract the new value from the original value:

   • So, $\text{Difference} = 10 - 8 = 2$

4. Divide the Difference by the Original Value: This shows how much lower the new value is.

   • In our case: $\text{Relative Decrease} = \frac{2}{10} = 0.2$

5. Convert to Percentage: Multiply by 100 to find the percentage.

   • So: $\text{Percentage Decrease} = 0.2 \times 100 = 20\%$

Why It Matters

Knowing how to calculate percentage changes is really helpful in everyday life! You might use it when shopping for discounts, noticing price changes, or even seeing if your salary goes up. Every time you see a change, you can use these steps to figure out the percentage increase or decrease.

Just remember the five steps for both increase and decrease. Soon enough, you'll be great at calculating percentages! It's not just about getting the numbers right; it's also about feeling good when you know you did it!