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Percent Change
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What you will learn from this videoWhat you will learn
- We’ll learn how to to solve multi-step percent problems.
- We’ll also learn how to calculate percent increase and percent decrease.
- And we'll see how this knowledge can help us buy items on sale, learn about different schools, and see how much our things are worth!
- Discussion Questions
Before Video
What is a percent? Can you give an example?ANSWERA percent is a ratio out of 100. 34% is 34 out of 100.
To write a percent as a fraction, write the number as the numerator over denominator 100, and then simplify. For example, 34% is [ggfrac]34/100[/ggfrac] or [ggfrac]17/50[/ggfrac]. To write a percent as a decimal, divide the number by 100. 34% = 0.34.
I change the percent to a decimal then multiply by the whole. 34% of 50 is 0.34 × 50 = 14.
percent = [ggfrac]part/whole[/ggfrac]. First, write a ratio of [ggfrac]part/whole[/ggfrac], and then divide to write it as a decimal. Multiply by 100 to write the value as a percent.
percent = [ggfrac]part/whole[/ggfrac], so whole = [ggfrac]part/percent[/ggfrac]. Write the percent as decimal, and then divide the part by the decimal to get the value of the whole.
After Video
How can you tell if the problem you want to solve is a percent increase or percent decrease problem?ANSWERI can look for keywords such as "more" or context-based words like “tax” or ”tip” to identify when the value is increasing. I can look for keywords such as "less" or context-based words like "discount" or "sale" to identify when the value is decreasing.
First, I calculate the part that represents the percent increase by multiplying the percent by the initial amount. Then, I add that amount to the original amount.
First, I calculate the part that represents the percent decrease by multiplying the percent by the initial amount. Then, I subtract that amount from the original amount.
First I subtract to find the difference between the original and increased amounts. Then I divide by the original amount to find the percent change as a decimal. Multiply by 100 to write it as a percent.
It is the same process as for an increased amount. First I subtract to find the difference between the original and decreased amounts. Then I divide by the original amount to find the percent change as a decimal. Multiply by 100 to write it as a percent.
- Vocabulary
- Ratio DEFINE
Shows the relationship between two quantities.
- Percent DEFINE
A ratio out of 100.
- Two-step problem DEFINE
A problem that requires two separate steps to solve.
- Percent increase DEFINE
When the value of a quantity increases by a certain percent, leading to a value that is more than 100% of the original value.
- Percent decrease DEFINE
When the value of a quantity is decreased by a certain percent, leading to a value that is less than 100% of the original value.
- Pie chart DEFINE
A special chart (data display) that divides a circle into sectors. Each sector shows a percent of the whole.
- Ratio DEFINE
- Reading Material
- Practice Word Problems
- Practice Number Problems
- Lesson Plan
- Teacher Guide