Percent of Change | Percent Increase and Decrease | Math with Mr. J

Summary

In this educational video, Mr. J teaches the concept of percent of change using two examples. The formula involves subtracting the old number from the new, dividing by the old number, and multiplying by 100 to get the percentage change. The video demonstrates a decrease from 50 to 34, resulting in a -32% change, and an increase from 10 to 22, yielding a 120% increase. The lesson emphasizes the importance of using the original number as the base for calculating the percentage change and interpreting the results as either an increase or decrease based on the sign of the result.

Takeaways

• 🔢 Calculate percent of change by taking the difference between the new and old numbers.
• 📉 For a decrease, subtract the old number from the new number to find the change, then divide by the old number and multiply by 100.
• 📈 For an increase, follow the same process but the result will be a positive percentage.
• ⚠️ Always divide by the original number to find the percentage change relative to the starting point.
• 👉 A negative result indicates a decrease, while a positive result indicates an increase.
• 📌 Moving the decimal point two places to the right converts the decimal to a percentage.
• 📋 The script provides two examples: one with a decrease from 50 to 34 and one with an increase from 10 to 22.
• 📐 The first example results in a -32% change, indicating a decrease.
• 📈 The second example results in a 120% change, indicating an increase.
• ✅ The script emphasizes checking the sign of the result to determine if there was an increase or decrease.

Q & A

What is the formula for calculating the percent of change?

The percent of change is calculated by taking the amount of change (new number minus old number), dividing by the old number, and multiplying by 100 to convert it to a percent.

How do you interpret a negative percent of change?

A negative percent of change indicates a decrease in value. It shows that the new number is lower than the old number.

In the first example, why is the result negative 32 percent?

The result is negative 32 percent because the value decreased from 50 to 34, and the negative sign shows the direction of change as a decrease.

What are two ways to express a percent of change that is a decrease?

You can express a decrease as either a negative percent (e.g., -32%) or as a positive percent followed by the word 'decrease' (e.g., 32% decrease).

What does it mean when the percent of change is positive?

A positive percent of change indicates an increase in value. It shows that the new number is higher than the old number.

In the second example, how is the percent increase calculated?

The percent increase is calculated by taking the new number (22) minus the old number (10), which gives 12. Then, 12 is divided by the old number (10) to get 1.2, which is multiplied by 100 to get a 120 percent increase.

How do you know if a percent of change represents an increase or a decrease?

A positive percent represents an increase, and a negative percent represents a decrease. You can also confirm by comparing the old and new numbers.

Why is it important to divide by the old or original number when calculating percent of change?

Dividing by the old or original number is important because it gives the percentage change relative to the starting point, showing how much the original value has changed.

What is the percent of change from 10 to 22 in the second example?

The percent of change from 10 to 22 is 120 percent, indicating an increase.

What does it mean if the result of the percent of change calculation is zero?

If the result is zero, it means there has been no change in value between the old and new numbers.