Rounding and place value (grade 3) · lesson

What a digit is worth

💡 A digit's value depends on its place: ones, tens, or hundreds.

In 952, the 9 is in the hundreds place. It is worth 900. The 5 is in the tens place. It is worth 50. The 2 is worth just 2.

To give a digit's value, write the digit and fill the places to its right with zeros.

🧠 Let's work it out

What is the 6 in 168 worth?

What do you think comes next?

💡 To round to the nearest ten, look at the ones digit: 5 or more rounds up, 4 or less rounds down.

First find the two tens the number sits between. 83 is between 80 and 90.

Then look at the ones digit. 3 is less than 5, so 83 rounds down to 80. 58 rounds up to 60.

Rounding up can change the tens and the hundreds. 397 is between 390 and 400, so it rounds up to 400.

🧠 Let's work it out

Round 241 to the nearest ten.

What do you think comes next?

💡 To round to the nearest hundred, look only at the tens digit.

Find the two hundreds the number sits between. 432 is between 400 and 500.

Look at the tens digit. 3 is less than 5, so 432 rounds down to 400. 172 has a 7 in the tens, so it rounds up to 200.

Don't round the ones first. Only the tens digit counts.

🧠 Let's work it out

Round 846 to the nearest hundred.

What do you think comes next?

💡 A number that is exactly halfway always rounds up.

35 is right in the middle of 30 and 40. It is not closer to either one.

The rule is to round up. So 35 rounds to 40, and 450 rounds to 500.

🧠 Let's work it out

Round 165 to the nearest ten.

What do you think comes next?