Скачать или смотреть Percentage increase and decrease

*CORE CONCEPT:*
Percentage increase and decrease calculations help express changes in values as percentages, allowing for practical problem-solving in everyday situations.

*TOPICS COVERED:*
When to use percentage increase calculations to determine growth.
When to use percentage decrease calculations to assess reductions.
How to identify original and new values for accurate calculations (B1 level).
How to apply percentage calculations to real-life examples.

*EXAMPLE SENTENCES:*
Example 1: If a score increases from 50 to 70, the percentage increase is calculated as (70 - 50) / 50 * 100 = 40%.
Example 2: A shirt costs $40 and is marked down to $30. The percentage decrease is calculated as (40 - 30) / 40 * 100 = 25%.
Example 3: A population grows from 200 to 250. The percentage increase is calculated as (250 - 200) / 200 * 100 = 25%.

*GRAMMAR RULES:*
Identify the original value → Identify the new value.
Calculate the difference → Divide the difference by the original value.
Multiply by 100 → Find the percentage change.

*COMMON ERRORS:*
Wrong: Confusing the original value with the new value → Right: Always identify the correct original and new values before starting calculations.
Wrong: Forgetting to multiply by 100 after dividing the difference → Right: Remember to multiply by 100 to convert the decimal to a percentage.
Wrong: Using the wrong formula, such as adding instead of subtracting → Right: Ensure you are subtracting the original from the new value when calculating increase.

*STUDENT QUESTIONS:*
How do I calculate percentage increase?
When do I use percentage decrease?
Is this example correct for percentage change?
What's the difference between increase and decrease in percentages?
How do I find the original value in percentage calculations?

*KEY CONCEPTS:*
Percentage increase, percentage decrease, B1 level, calculations, real-life examples, practical problems.