Question Video: Understanding That Three-Digit Numbers Can Be Represented with Groups of Tens and Ones Mathematics • 2nd Grade

Find the missing three-digit number.


Video Transcript

Find the missing three-digit number.

To help us answer this question, we’re shown a part–whole model. We’re given both parts, but we don’t know the whole. And we’re told that this is a missing three-digit number. But wait a moment! We know that it’s possible to have a three-digit number without any tens, also without any ones, or even both. But it’s not possible to have a three-digit number without any hundreds. And yet, if we look at the two parts that make up our part–whole model, we can see that one of them represents a number of tens and the other a number of ones. Where are the hundreds? What is this mystery three-digit number?

Let’s try modeling our part–whole model using a place value grid. Here are our five ones and 32 10s. But if we were to try writing this using digits, we know that we could write a five in the ones place. But we also know we can’t write two digits in the tens place. We’re going to need to regroup our number. Although we can show this three-digit number as 32 10s and five ones, if we want to write it using three digits, we’re going to have to change some of our groups of tens. We know that 10 10s are the same as one 100. And in the number 32 10s, we’ve got three lots of 10 10s. And so we can exchange them for three 100s. We can write our number as three 100s, two 10s, five ones.

We’ve used our knowledge of place value here to exchange some of the many tens that we had for hundreds. 32 10s are the same as three 100s and two 10s. And if we also include the five ones, this makes our missing three-digit number 325.

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