Have you ever ordered lunch and wondered what to tip a waiter or waitress? Well, look at what happened to Sam and Kaitlin.

Sam and Kaitlin went to a small diner for lunch. They had an hour break from work at the supermarket and so it was the perfect time to get a bite to each.

Sam had a grilled cheese sandwich with fries, and Kaitlin had soup and half a turkey sandwich.

Their total bill was $12.90.

Sam and Kaitlin weren't sure how much to tip the waitress. Do you know?

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This Concept is all about how to calculate and estimate tips. By the end of it, you will know how to help them with this dilemma.
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### Guidance

When you eat in a restaurant, you usually pay a tip to the server.
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A
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tip
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**is a percent of the cost of the meal. It is also called a**

*gratuity.*When ordering out, you can use estimation to figure out the tip for the server. It is customary to give the server 15% of the total of the meal.

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You can use what you have learned about percents to estimate tips.
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John ate out for lunch. His total bill came to $12.00. How much should he tip the server?

How can we figure this out?

We know that we need to find approximately 15% of $12.00. 15% is between 10% and 20%. It is easy to find 10% because we can multiply by .10 or move the decimal point one place to the left in the total.

This would mean that 10% of $12.00 is $1.20. If 10% of $12.00 is 1.20, then 20% is 2.40.

We want to choose a number between these two amounts for 15%.

A reasonable estimate would be $1.75 or $2.00.Sometimes people find it easier to calculate 20% using mental math so they often give the server a larger tip because it is easier to figure out!

Now it is your turn. Estimate the following tips.

#### Example A

A tip on $25.00

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Solution: $3.50 - $3.75
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#### Example B

A tip on $18.00

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Solution: $2.50 - $3.00
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#### Example C

A tip on $36.50

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Solution: $5.50 - $6.00
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Now back to Sam and Kaitlin and lunch at the diner. Here is the original problem once again.

Sam and Kaitlin went to a small diner for lunch. They had an hour break from work at the supermarket and so it was the perfect time to get a bite to each.

Sam had a grilled cheese sandwich with fries, and Kaitlin had soup and half a turkey sandwich.

Their total bill was $12.90.

Sam and Kaitlin weren't sure how much to tip the waitress.

To estimate this tip, we can first round up to the nearest whole dollar.

$12.90 rounds up to $13.00.

To tip 15%, we can estimate that 10% is $1.30 and then estimate half of that.

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Our answer is $2.00. This is a reasonable tip.
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### Vocabulary

Here are the vocabulary words in this Concept.

- Percent
- a part of a whole 100, written using a % sign.

- Proportion
- two equal ratios.

- Sales Tax
- a percent added to a total

- Discount
- an amount taken off of an original price

- Tip
- 15 – 20% of a total bill paid to a server

- Gratuity
- another word for tip

### Guided Practice

Here is one for you to try on your own.

Kelly went to lunch. Her total bill was $29.85. What should she tip the waiter?

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Answer
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To do this, we can first round the bill up to the nearest whole number.

$29.85 rounds up to $30.00

Next we can use mental math to take 10% of that number and then half of that gets us to 15%.

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Our estimate is $4.50.
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### Video Review

Here is a video for review.

Khan Academy: Rounding to Estimate Sums

http://www.mathplayground.com/howto_percentwp.html - This is a math playground video on how to estimate tips.

### Practice

Directions: Estimate the following tips.

1. A tip on $10.00

2. A tip on $18.00

3. A tip on $25.00

4. A tip on $30.00

5. A tip on $15.00

6. A tip on $47.00

7. A tip on $89.00

8. A tip on $121.00

9. A tip on $135.00

10. A tip on $112.50

11. A tip on $127.75

12. A tip on $135.50

13. A tip on $97.78

14. A tip on $88.67

15. A tip on $99.20