1. Percents

2. Percent Change
A percent change indicates how much a quantity increases or decreases with respect to the original amount.
When an amount increases from its original amount, it is called a percent increase.
 When an amount decreases from its original amount, it is called a percent decrease.

3. Original amount: $12 New amount: $4
Percent Change
Identify the percent change as an increase or decrease. Then find the percent of change.
A store charges $12 for a shirt. The price of the shirt decreased to $4 at the end of season.
Solution: The percent change is a decrease since the new amount is less than the original amount.
Original amount: $ New amount: $4
The percent decrease is 75%. The sale price is 25% of the regular price.

4. Percent Change
Identify the percent change as an increase or decrease. Then find the percent of change.
A buyer for a store purchases jeans at $50 each. He plans to sell them for $60 each.
Solution: The percent change is an increase since the new amount is greater than the original amount.
Original amount: $ New amount: $60
The percent increase is 20%. The price of the jeans increased 20%.

5. Percent Change
The price of a token to ride a subway is $ Next month, the price of a token will be $ Find the percent change.
Solution: The percent change is an increase since the new amount is greater than the original amount.
Original amount: $ New amount: $1.95
The percent increase is 30%. The price of the token will increase 30%.

6. Original amount: $13.98 New amount: $10.00
Percent Change
A CD that costs $13.98 is on sale for $10. Find the percent change. Round your answer to the nearest percent.
Solution: The percent change is a decrease since the new amount is less than the original amount.
Original amount: $ New amount: $10.00
The percent increase is 28%. The sale price is 72% of the regular price.

7. The price to remodel a bathroom in 2012 is $17,700.
Percent Change
If the original amount and the percent of change are known, you can find the new amount.
For a percent change increase, multiply the original amount by 100% + the percent of change.
The price to remodel a bathroom is $15,000 in In 2012, the price to remodel had increased by 18%. Find the price to remodel a bathroom in 2012.
Solution: The new price is an increase from the original price. To find the new price, multiply 15,000 by (100+18)%.
The price to remodel a bathroom in 2012 is $17,700.

8. The sale price of the skirt is $17.50.
Percent Change
For a percent of change decrease, multiply the original amount by 100% minus (–) the percent of change.
The price of a skirt is $25. Find the sale price if the store is having a $30% off sale.
Solution: The sale price is a decrease from the original price. To find the sale price, multiply 25 by (100 – 30)%.
The sale price of the skirt is $17.50.

9. The amount of interest earned is $960.
Simple Interest
To calculate simple interest, use the formula I = prt, where I = interest, p = principal, r = interest rate, and t = time in years.
I = prt
Find the amount of interest earned on an investment of $4,000 at 8% for 3 years.
Solution:
The amount of interest earned is $960.

10. The amount of interest earned is $420.
Simple Interest
To calculate simple interest, use the formula I = prt, where I = interest, p = principal, r = interest rate, and t = time in years.
I = prt
Find the amount of interest earned on an investment of $3,500 at 3% for 4 years.
Solution:
The amount of interest earned is $420.

11. Simple Interest
You can work backward to find the principal if you know the interest earned, the interest rate, and the amount of time invested.
I = prt
 You earned $120 interest on an investment. How much did you originally invest if the interest rate was 5% interest for 2 years?
Solution:
The amount of the original investment was $1,200.

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