Finding the Original Amount and Amount of Change Using Proportions and Equations

This video tutorial teaches how to find the original amount and the amount of change given the percent change and final amount using proportions and equations. It uses a practical example of calculating the pre-tax price of a couch and the sales tax from a given final price. The lesson reviews solving proportions and equations, emphasizing the difference between percent change and the actual amount of change. It provides two methods: using proportions and using equations, to solve for the original amount and the tax.

What is the key information needed to find the original price of an item before tax?

• The original price and the tax amount

• The original price and the discount rate

• The final price and the percentage of tax

• The final price and the discount amount

Which method can be used to solve a proportion?

• Adding percentages

• Cross products

• Using inverse operations

• Subtracting percentages

What is a common mistake when calculating percentage increase or decrease?

• Not balancing both sides of an equation

• Forgetting to convert percentages to decimals

• Using cross products incorrectly

• Confusing the percentage with the actual amount

How do you find the original amount using proportions?

• By adding the percentage to the final amount

• By multiplying the final amount by the percentage

• By subtracting the percentage from the final amount

• By setting up a proportion and solving for the unknown

What is the original price of the couch if the final price is $600 including 8% tax?

• $600

• $648

• $555.56

• $44.44

How do you convert a percentage to a decimal?

• By multiplying by 100

• By dividing by 10

• By moving the decimal two places to the right

• By moving the decimal two places to the left

What equation represents the final amount if the original amount is x and the tax is 8%?

• x / 0.08 = final amount

• x + 0.08x = final amount

• x - 0.08x = final amount

• x * 0.08 = final amount