Video: Dividing Decimal Numbers by 10, 100, and 1000

Complete following the table.

04:27

Video Transcript

Complete the following table. We have to divide the number 231.72 by 10, 100, and 1000.

Let’s start by dividing 231.72 by 10. What happens to a number when we divide it by 10? Well, the number will get 10 times smaller. 231 rounded to the nearest 100 is 200. 200 divided by 10 is 20. So, we can estimate that our answer will be 20 something. We know that 200 divided by 10 is 20. So, the two digit is now worth two 10s instead of two 100s. And we can see that the digit has moved one place to the right. Three 10s, or 30, divided by 10 is three. So, the three becomes three ones instead of three 10s. The digit has moved one place to the right. And this is where the decimal point should be.

So, already we can see that our estimate was correct. Our number is 20 something, 23. One divided by 10 becomes one tenth, or 0.1. And of course, this digit has moved one place to the right. And in the same way, we can write the last two digits, the seven and the two. So, 231.72 divided by 10 is 23.172. We can write this number in the first column, 23.172.

In the next column, we have to write the answer to 231.72 divided by 100. Well, 100 is 10 times more than 10. We’ve already divided our number by 10. If we divide it by 10 again, that’s the same as dividing by 100. And we know that when we divide a number by 10, it gets 10 times smaller and the digits move one place to the right. So, 231.72 divided by 100 is 2.3172. Or we could say that 23.172 divided by 10 is 2.3172. So, we can write the answer in the second column, 2.3172.

And in the final column, we have to write 231.72 divided by 1000. We know that 1000 is 10 times greater than 100. So, to divide by 1000, we just need to divide 2.3172 by 10. Dividing by 1000 is the same as dividing by 10 then dividing by 10 and then dividing by 10 again. And we know that when we divide by 10, the digits shift one place to the right. We can see the digits have moved one place to the right.

231.72 divided by 1000 is 0.23172. So, we can write the answer in the final column, 0.23172. This is the same as dividing 2.3172 by 10. The missing numbers from the table are 23.172. This is 231.72 divided by 10. The next missing number is 2.3172, which is 231.72 divided by 100. And 231.72 divided by 1000 is 0.23172. We used our knowledge of place value to help us find the missing numbers.

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