Percentage

To calculate a value from a base amount and percent, divide the percent by 100 to get a decimal, and multiply that by the base amount. This is useful for calculating tips, taxes, commissions, etc.
For example, your restaurant bill is $25, and you want to leave a 15% tip, which is extra money given to service workers. To calculate the tip amount, do the following: 
base    = $25
percent = 15
decimal = 15 ÷ 100 = 0.15
tip     = $25 × 0.15 = $3.75

Exercise 1 of 6

Most states have a sales tax, which is a tax paid when buying something, and is a percentage of the purchase amount. Taxes pay for roads, schools, and other government services. You bought a $20 item, and sales tax is 8.75%. What is the tax amount?

Exercise 2 of 6

Your restaurant bill is $30, you want to leave an 18% tip, and sales tax is 9.5%. What is the total cost?

Exercise 3 of 6

Most countries have an income tax, which is a tax paid on money earned in a year, and is a percentage of the earned amount. You earned $50,000, and income tax is 8.48%. What is the tax amount?

Exercise 4 of 6

You earned $100,000, and income tax is $14.77%. What is the amount you keep after deducting income tax?

Exercise 5 of 6

When real estate agents help somebody buy or sell a house, they earn a commission, which is a percentage of the sale price. You are a real estate agent who sold a house for $416,000 for a 3% commission. What is the amount you earned?

Exercise 6 of 6

Companies can sell stock, which represent partial ownership in the company. Stocks are sold as a price per share, and it can change based on the company's performance. For example, if you buy a stock, and its share price goes up 10%, you earn 10% of the purchase price. In 1997, Amazon sold stock to the public, and over the next 25 years, its share price went up 250,000%. If you had bought $1,000 worth of Amazon stock during their initial sale, how much would you have earned?

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