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Rounding using a number line (tens)

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Rounding using a number line (tens)
CCSS.MATH.CONTENT.3.NBT.A.1

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Rounding to the Nearest 10 on a Number Line

This video shows how to round to the nearest ten on a number line. How to set up up a number line for rounding, and when to round up or round down is covered in the video. There are also rounding to the nearest ten on a number line worksheets below for further practice.

Transcript Rounding using a number line (tens)

Skylar and Henry are participating in a frisbee competition, where the top three finishers will receive all you can carry caramel apples! They each get one throw. The spot where the frisbee lands is rounded to the nearest ten, and this becomes their score. Skylar steps up for her throw. Now it is Henry's turn. Their fierce competitor, Benji, throws last. To calculate their scores we can use rounding to the nearest ten on a number line. When rounding to the nearest ten on a number line, first identify the number you are rounding. Next, set up the lesser tens value on the left side and the higher tens value on the right side. Then fill in all the numbers between the tens. The number line is ready, so we plot the number we are rounding on it. If the number is below halfway, we round down to the nearest ten, and if the number is halfway or above, we round up to the nearest ten. Let's practice with Benji's throw. Here is where Benji's throw landed. First identify the number we are using, which is forty-five. The lesser tens value is forty, so write it at the beginning, and the higher tens value is fifty, so write it at the end. Now fill in the number line with all the numbers between forty and fifty. Benji scored forty-five, so we can plot it here on the number line. We can see that forty-five is at the halfway point on the number line, so we round up to fifty. Forty-five rounded to the nearest ten is fifty. Let's see if you can help calculate Skylar and Henry's score! Here is where Skylar's frisbee landed. Can you identify the number? It is seventy-six. What is the lesser tens value and higher tens value of seventy-six? The lesser tens value is seventy, and the higher tens value is eighty. Now we fill in all the numbers between seventy and eighty. Can you remember the next step? We plot Skylar's frisbee throw, so seventy-six goes here. Now we need to decide if we round up, or round down. Which should we do for Skylar's score? Seventy-six is over halfway on the number line, so we round up to the nearest ten. Seventy-six rounded to the nearest ten is eighty. Now let's calculate Henry's score. Here is where Henry's frisbee landed. What is the number? It is sixty-four. What is the lesser tens value and higher tens value of sixty-four? The lesser tens value is sixty and the higher tens value is seventy. Now we fill in all the numbers between sixty and seventy. What is the next step? We plot Henry's frisbee throw, so sixty-four goes here. Now we need to decide if we round up, or round down. Which should we choose for Henry's score? Sixty-four is below halfway on the number line, so we round down to the nearest ten. Sixty-four rounded to the nearest ten is sixty. Remember, to round to the nearest ten on a number line, first identify the number you are rounding. Next, set up the lesser tens value on the left side and the higher tens value on the right side. Then fill in all the numbers between the tens. Now the number line is ready, we plot the number we are rounding on the number line. If the number is below halfway we round down to the nearest ten, and if the number is halfway or above we round up to the nearest ten. Well, it looks like Skylar was the overall winner. Great job, Skylar. But don't forget, everyone in the top three gets all you can carry caramel apples. Wow, Benji and Henry, you both sure have a lot of caramel apples there! Of course, Skylar, cunning as always.

Rounding using a number line (tens) exercise

Would you like to apply the knowledge you’ve learned? You can review and practice it with the tasks for the video Rounding using a number line (tens).
  • Round the numbers to the nearest 10.

    Hints

    If the ones digit is 5 or above we round up or if it is 4 or below we round down.

    Let's look at the number 17.

    We look at the ones digit which is 7.

    Since 7 is above 5 we round up to the next 10. The next ten is 20.

    Solution

    Since we are rounding to the nearest ten we look at the digit before this. This is the ones digit. If the digit is 5 or above, we round up. If the digit is 4 or below we round down.

    68 = 70

    56 = 60

    44 = 40

    45 = 50

  • Place the given numbers next to their nearest 10.

    Hints

    Look at the number. Is the ones number 5 or above? If so we round up to the next ten.

    Is the ones number 4 or below? If so we round down.

    In this example, the ones digit is a 4. Since it is 4 or below, we round down. Our answer is 20.

    Solution

    24 → 20

    35 → 40

    55 → 60

    78 → 80

  • Round the numbers to the nearest ten.

    Hints

    When rounding to the nearest ten we look at the ones digit to identify which way we round.

    Is the digit 5 or above? If yes then we round up.

    Is the digit 4 or below? If yes then we round down.

    If we use the number 17 as an example.

    First we look at the ones digit. This is 7. Since this is 5 or above we round up to the next ten.

    Use a number line to help you.

    Solution

    Remember if the ones digit number is 5 or more, we round up to the next ten.

    If the ones digit is 4 or less we round down.

  • Can you help check Henry's final score card?

    Hints

    Look at the ones digit in the number. Is it 5 and above or 4 and below?

    If the ones digit is 5 or above we round up. If it is 4 or below we round down.

    Using this example, the ones digit is 5 or above so we round up to the next ten which is 80.

    Solution

    Remember, when rounding to the nearest ten you look at the digit before. This is the ones digit. If the ones digit is 5 or above we round up. If the ones digit is 4 or below we round down. Please see the correct answers below:

    75 $\rightarrow$ 80

    99 $\rightarrow$ 100

    111 $\rightarrow$ 110

  • Round the numbers to the nearest 10.

    Hints

    Is the ones digit 5 or above? If so we round up.

    Is the ones digit 4 or below? If so we round down.

    Identify the ones digit.

    Use the number line to help you. Identify where the 5 is, it is halfway.

    Is the number you're rounding sitting at the halfway point or higher? Round up.

    Is your number sitting below the halfway mark? Round down.

    Solution

    25 - as the digit in the ones is 5 we round it up to the next ten.

    43 - as the digit in the ones is below 5 we keep the same ten.

    77 - as the digit in the ones is more than 5 we round it up to the next ten.

    54 - as the digit in the ones is below 5 we keep the tens the same.

  • Can you help complete the order?

    Hints

    When rounding to the nearest 10 we look at the the digit value to the right which is the ones digit. If this is 5 or above we round up to the next ten. If it is 4 or below we keep the same tens number.

    Is the ones digit 5 or above? Or is it 4 or below?

    First let's identify the tens digit.

    We know we will either be rounding to 230 or 240.

    In this example, to round to the nearest 10 we must look at the ones digit. Is it 5 and above or 4 and below?

    Solution

    When rounding to the nearest 10 we look at the digit value to the right which is the ones digit. If this is 5 or above we round up to the next ten. If it is 4 or below we keep the same tens number.