Estimation

Brainstorm

Brainstorm

Take two minutes to silently reflect on the following two questions:

1. Why is estimation important?
2. When do we use estimation in our daily life?

Turn to a partner, if possible, and share your thoughts with each other.

In your daily life, imagine if you could easily estimate:

• how much something that you want to buy will cost
• which item is the best value for your money
• the size, areas, and angles of things
• quickly guess how many people are in a room at a given time
• how many people are in a room at a given time

We’re not talking about exact numbers here, but answers that are close enough to be useful in your daily life.

Rounding by place value

Rounding is a useful estimation strategy. Let’s explore rounding by place value.

Explore the video below to learn more about rounding numbers.

Round 3,456 to the nearest thousand, nearest hundred, and nearest ten.

• What do you notice as you round by each place value?

Use the anchor chart below or an organizer of your choice to help you round.

Click on the ‘Answer’ button to reveal the rounding answers.

Answer

If you use smaller place values, such as rounding to the nearest ten, you get closer to the exact number.

If you use larger place values, such as rounding to the nearest thousand, you get further away from the exact number.

Try a few more:

Student Success

Think-Pair-Share

Math congress

Let’s explore the connection between estimation and mental math. Mental math is a calculation that you do in your head without using pencil and paper, calculators, or other aids. Mental math is often used to calculate and estimate quickly, such as when multiplying, dividing, or calculating larger numbers.

Consider this scenario:

A shop owner runs a small business and pays $4,744.00 every month for rent at their boutique wellness store. The shop owner also pays $3,246.00 every month for rent at the place they live.

How much money does the shop owner spend per month on rent at both locations?

1. Record your estimate first (use rounding!)
2. Now find the exact answer using a mental math strategy.
3. How close was your estimate to your sum?
4. How much money does the shop owner spend per year on rent? How did you solve this?

If possible, discuss your estimation strategies and answers with a partner.

Explore the differences between the estimated sum depending on how the numbers were rounded.

For example: rounding to the nearest thousand would be $5,000 + $3,000 = $8,000 compared to rounding to the nearest hundred would be $4,700 + $3,200 = $7,900.

Do you notice that the second estimate is closer to the exact sum of $7,990 per month?

1. If possible, discuss the mental math strategies that you used with a partner.

Note to teachers: See your teacher guide for collaboration tools, ideas and suggestions.

Task 1

Now it is your opportunity to apply what you learned in the Action section to your own scenario. Use the shop owner question from the Action section to create your own business and rent costs per month for two separate properties. Be creative!

Once you have your scenario, just as before, you can then answer the following questions.

1. Record your estimate first (use rounding!)
2. Now find the exact answer using a mental math strategy.
3. How close was your estimate to your sum?
4. How much money does the shop owner spend per year on rent? How did you solve this?

Record your scenario, strategies, and responses in an audio recording, on paper, or on the computer.

Task 2

If you have a number in the thousands, as in the shop owner scenario in the Action section, do you prefer to round to the nearest ten, hundred, or thousand? Why?

Record your response in an audio recording, on paper, or on the computer.

Reflection

As you read through these descriptions, which sentence best describes how you are feeling about your understanding of this learning activity? Press the button that is beside this sentence.

I feel...

I have an excellent understanding of the concepts I have a very good understanding of the concepts I have some understanding but need to review some more my understanding of the concepts needs a lot more work

Now, record your ideas using a voice recorder, speech-to-text, or writing tool.