
- Percentage Increase & Decrease
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- Finding the final amount given the original amount and a percentage increase or decrease
- Finding the sale price given the original price and percent discount
- Finding the sale price without a calculator given the original price and percent discount
- Finding the total cost including tax or markup
- Finding the original amount given the result of a percentage increase or decrease
- Finding the original price given the sale price and percent discount
- Comparing discounts
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Finding the original amount given the result of a percentage increase or decrease
In this lesson, we learn how to find the original amount, given result of a percent increase or decrease.
Rules to find the original amount given the result of a percentage increase or decrease
First consider the unknown original amount as ‘x’.
Then consider the percent rate of increase or decrease
To find the increase or decrease, multiply the rate by the original amount ‘x’.
To find the final amount, add or subtract the increase or decrease to the original amount ‘x’ and equate this to given final amount.
Solve the equation and find the original amount ‘x’.
After a 25% increase, a TV was $750. Find the original price
Solution
Step 1:
Let the original amount be = x
Percent increase = 25%
Step 2:
Increase in price = 25% of x = 0.25 × x = 0.25x
Final amount = Original amount + increase = x + 0.25x = 1.25x
Step 3:
Final amount = $750 = 1.25x
Solving for x
x = $\frac{750}{1.25} =$ $600
So, original amount = $600
After a 60% discount, a lawn chair was $105. Find the original price
Solution
Step 1:
Let the original amount be = x
Percent increase = 60%
Step 2:
Decrease in price = 60% of x = 0.60 × x = 0.6x
Final amount = Original amount − Decrease = x − 0.6x = 0.4x
Step 3:
Final amount = $105 = 0.4x
Solving for x
x = $\frac{105}{0.4} =$ $262.50
So, original amount = $262.50