Rounding Decimals: Mastering the Tricky Nines!

Mathematics Grades 5th Grade 6:22 Video
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Lesson Description

Learn how to round decimals, especially when you have a 9 in the place you're rounding! This lesson uses a fun video and examples to help you understand regrouping and rounding strategies.

Video Resource

How to Round Up a 9 | Rounding Decimals | Math with Mr. J

Math with Mr. J

Duration: 6:22
Watch on YouTube

Key Concepts

  • Place Value in Decimals
  • Rounding Rules (5 or more, round up)
  • Regrouping/Carrying (Similar to addition)
  • Rounding up a 9
  • Estimating Decimal Values

Learning Objectives

  • Students will be able to identify the place value of digits in a decimal number.
  • Students will be able to round decimals to the nearest tenth, hundredth, or whole number.
  • Students will be able to accurately round decimals when the digit to be rounded up is a 9.
  • Students will be able to explain the regrouping process when rounding up a 9.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the basics of rounding. Ask students what they already know about rounding whole numbers. Then, introduce the idea of rounding decimals and how it's similar but slightly different.
  • Video Viewing (10 mins)
    Play the YouTube video "How to Round Up a 9 | Rounding Decimals | Math with Mr. J." Instruct students to pay close attention to the two methods Mr. J uses for rounding up a 9: regrouping and the 'two-digit' look.
  • Guided Practice (15 mins)
    Work through several examples as a class, focusing on the cases where rounding up a 9 is required. Use both methods presented in the video (regrouping and the two-digit look). Start with easier examples and gradually increase the difficulty. For example: 0.29, 4.99, 12.795.
  • Independent Practice (15 mins)
    Provide students with a worksheet or online activity with various decimal numbers to round. Include problems that require rounding up a 9 in different place values. Monitor students' progress and provide assistance as needed.
  • Wrap-up and Assessment (5 mins)
    Review the key concepts of the lesson. Administer the multiple-choice or fill-in-the-blank quiz to assess student understanding.

Interactive Exercises

  • Number Line Rounding
    Draw a number line on the board (or use a digital whiteboard). Place a decimal number on the number line. Ask students to identify which whole number or tenth the decimal is closest to. This visual representation can help solidify their understanding of rounding.
  • Decimal Rounding Game
    Create a simple game where students take turns rolling a die to generate a decimal number. Then, they must round the number to a specified place value (e.g., nearest tenth, hundredth) within a given time limit. Award points for correct answers.

Discussion Questions

  • Why is it important to understand place value when rounding decimals?
  • How is rounding decimals similar to rounding whole numbers?
  • What are some real-life situations where you might need to round decimals?
  • Explain in your own words how to round up a 9 in a decimal number.

Skills Developed

  • Decimal Place Value Understanding
  • Rounding Skills
  • Problem-Solving
  • Critical Thinking
  • Number Sense

Multiple Choice Questions

Question 1:

What is the value of the 9 in the number 3.492?

Correct Answer: 9 hundredths

Question 2:

When rounding, if the number to the right is 5 or more, you should:

Correct Answer: Round up

Question 3:

What is 2.9 rounded to the nearest whole number?

Correct Answer: 3

Question 4:

What is 0.89 rounded to the nearest tenth?

Correct Answer: 0.9

Question 5:

What is 1.399 rounded to the nearest hundredth?

Correct Answer: 1.40

Question 6:

Which number is in the tenths place in 12.345?

Correct Answer: 3

Question 7:

Which number is in the hundredths place in 9.071?

Correct Answer: 7

Question 8:

When rounding, you only look at the number immediately to the ________ of the digit you are rounding.

Correct Answer: Right

Question 9:

If you round 0.49 to the nearest tenth, what do you get?

Correct Answer: 0.5

Question 10:

Which of these numbers, when rounded to the nearest whole number, would become 10?

Correct Answer: 9.4

Fill in the Blank Questions

Question 1:

Rounding helps you find a number that is close to the real number, which is also called an ________.

Correct Answer: estimate

Question 2:

If the number to the right of the place you are rounding is 5 or more, you must ________ the digit.

Correct Answer: round up

Question 3:

When rounding to the nearest tenth, you look at the ________ place.

Correct Answer: hundredths

Question 4:

When you round up a 9, it turns into a ________.

Correct Answer: 0

Question 5:

The number 3.14 rounded to the nearest whole number is ________.

Correct Answer: 3

Question 6:

The number 7.9 rounded to the nearest whole number is ________.

Correct Answer: 8

Question 7:

The digit in the tenths place in the number 15.62 is ________.

Correct Answer: 6

Question 8:

The digit in the hundredths place in the number 2.481 is ________.

Correct Answer: 8

Question 9:

4.5 rounded to the nearest whole number is ________.

Correct Answer: 5

Question 10:

When rounding decimals, understanding ________ ________ is very important.

Correct Answer: place value

Educational Standards

5.N.1.2:Read, write, and represent decimals using place value to describe decimal numbers including fractional numbers as small as thousandths and whole numbers up to seven digits. 5.N.3.1:Estimate sums and differences of fractions with like and unlike denominators, mixed numbers, and decimals to assess the reasonableness of the results.

Teaching Materials

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