Video: Adding Two Numbers up to 999

Which number is 468 more than 421?


Video Transcript

Which number is 468 more than 421?

Let’s sketch a bar model to help us understand what we need to do to find the answer here. This bar could represent the number 421. Here’s 468 more than 421. And this value here is the number that is 468 more than 421. It’s the total of both numbers. To find the answer, we need to add 421 and 468 together. We’re going to add the ones, the tens, and the hundreds digits in these numbers separately. And to help us do this, we can set out the numbers vertically.

421 is made up of four hundreds, two tens, and one one. And we’re finding 468 more than this, which is also made up of four hundreds, but this time, six tens and eight ones. Let’s start by adding our ones together. 421 has one one and 468 has eight ones. One plus eight equals nine ones altogether. And we can model this answer by putting our two lots of ones cubes together. One plus eight equals nine. Now, let’s think about our tens digits. 421 contains a two in the tens place. That’s where we get the number 20 from. And by finding 468 more than 421, we need to add another six tens. So what’s two tens plus six tens?

Well, we know two plus six equals eight. So two tens plus six tens equals eight tens or 80. Again, let’s combine our tens rods this time to show that they make eight tens altogether. Two tens plus six tens equals eight tens. Finally, it’s time to add our hundreds digits together. Both numbers have the digit four in the hundreds place. 400 plus 400 equals 800. And if we combine our hundreds blocks together, we can see that we have 800 altogether. 400 plus 400 equals 800.

We’ve used column addition. And we’ve also used base ten blocks to help us find the answer. When we add 421 and 468 together, we get a number with eight hundreds, eight tens, and nine ones. So we can say that the number that is 468 more than 421 is 889.

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