Lesson Video: Modeling Three-Digit Numbers Mathematics • 2nd Grade

Video Transcript

Modeling Three-Digit Numbers

In this video, we will learn how to count how many objects there are when objects are arranged in groups of 100, 10, and one.

This is the number 358. 358 is a three-digit number. Its first digit is a three. Its second digit is a five. And its third digit is eight. The position of each digit tells us its value. The three digit in 358 is worth three 100s, so the three represents 300. Five is the tens digit. The five is worth 50. And the eight digit is in the ones column. It’s worth eight ones.

But what would happen if we changed the position of the digits? Now the eight digit is in the hundreds place, so the eight digit is worth 800. The three digit is now worth three 10s or 30. And the five digit is worth five ones. We made the number 835. If we change the position of the digits, we change their value. We could model the number 835 using place-value counters. We need eight 100s, three 10s, and five ones. We’ve modeled the number 835.

These pencils have been grouped together. Each box contains 100 pencils. Each pot contains 10 pencils. And this single pencil is grouped by one. We have 100s, 10s, and ones. We need to count the total number of pencils. We can use a number line to help us count in 100s, 10s, and ones. We know we have two boxes which each contain 100 pencils. So we need to count forward first in 100s. As there are two boxes of pencils, we need to count forward in 100s twice. 100, 200.

Next, we need to count the pots with 10 pencils. There are three pots, so we need to count forward in 10s three times. So we’re going to start at 200 and count forward 10: 210, 220, 230. Now we just need to count forward in ones: 231. We counted in 100s, 10s, and ones. There are 231 pencils. Let’s practice counting in 100s, 10s, and ones with some questions.

Mason wants to know how many items of fruit he bought. Answer the questions to help him. He counts in 100s to find how many cherries he has. Then, he counts in 10s to add the watermelons. What three numbers should he say after 310? 100, 200, 300, 310, what, what, what.

In this question, we’re being asked to count in 100s and 10s to help Mason find out how many pieces of fruit he has. The cherries come in boxes of 100. So he started to count his cherries in 100s. 100, 200, 300. Mason also bought some watermelons, which come in boxes of 10. So we need to start counting at 300 and keep on counting in 10s. 300, 310, 320, 330, 340. Now, we know that Mason had 340 pieces of fruit, the three numbers that he should say after 310 are 320, 330, and 340.

First, Mason counted his cherries in 100s: 100, 200, 300. He counted his watermelons in 10s: 310, 320, 330, 340. So the missing numbers are 320, 330, and 340.

He also bought some oranges. Count on to figure out how many pieces of fruit he has in total.

We know that Mason bought three boxes of cherries. Each box contained 100 cherries. And he bought four boxes of melons, and the melons came in boxes of 10. So we can start counting at 100. 100, 200, 300. We need to keep on counting in 10s now because the watermelons came in boxes of 10. 310, 320, 330, 340. And we can count the oranges in ones. The oranges are single pieces of fruit. They haven’t been grouped together in 10s or 100s. We count these as ones. 341, 342, 343, 344, 345, 346, 347. We counted in 100s, 10s, and ones. The total number of pieces of fruit that Mason bought is 347.

Count the marbles.

In this question, we’re shown some different jars of marbles, these two jars of marbles both contain 100 marbles. These three jars each contain 10 marbles. These marbles haven’t been grouped. We count these as ones. So to count the marbles, we need to count in 100s, 10s, and ones. Let’s start counting in 100s. 100, 200. We counted in 100s twice because there are two jars of marbles and each jar contains 100 marbles.

Next, we need to count forward in 10s because we’ve got three jars of marbles each containing 10 marbles. We’re going to start at 200 and count forward in 10s three times. 210, 220, 230. Now what we need to do is count forward in ones. 231, 232. We counted the marbles in 100s, 10s, and ones. There were 232 marbles.

There are 100 balls in each bag. How many balls are there?

We can see that there are three bags of balls. And we know that each bag contains 100 balls. So to count the number of balls in the bags, we need to count in 100s. 100, 200, 300. But that isn’t the total number of balls. We have to count these ones too. They haven’t been grouped, so we can count these as ones. There are four ones. 301, 302, 303, 304. First, we counted in 100s. Then, we counted in ones. We had three 100s and four ones.

Did you notice that there were no 10s, only 100s and ones? The total number of balls is 304.

Count in 100s and 10s to write the missing numbers. 100, 200, 300, what, 410, what and what.

In this question, we’re shown some place-value blocks. And we need to count those in 100s. 100, 200, 300, 400. We know the first missing number is 400. Now we need to continue counting in 10s: 410, 420, 430. 100, 200, 300, 400, 410, 420, 430. The missing numbers are 400, 420, and 430.

What have we learned in this video? We’ve learned how to count on to find the total when objects are grouped in 100s, 10s, and ones. We’ve also learned how to model three-digit numbers using place-value equipment.