Video: Multiplying and Dividing Decimal Numbers

The numbers in the first row of the table are multiplied by the multiplier to get the numbers in the bottom row. Complete the missing numbers from left to right.

03:34

Video Transcript

The numbers in the first row of the table are multiplied by the multiplier to get the numbers in the bottom row. Complete the missing numbers from left to right.

Let’s read this problem again more slowly to try to understand what it’s describing. Firstly, we’re told that the numbers in the first row of the table are multiplied by their multiplier. A multiplier is simply a number that we’re multiplying by. We can see the multiplier in our table here. It’s this missing number. And our problem tells us that the numbers in the first row of the table are multiplied by this unknown number to get the numbers in the bottom row.

In other words, 1.3 multiplied by something equals 3.9. And also 3.5 times something equals something. Here’s our second missing number. This missing number is going to be very hard to find unless we find the multiplier first. And that’s why we’re asked to complete the missing numbers from left to right. We need to find the multiplier. And then, we can find this final missing number.

So, how can we find what the multiplier is? Well, as we’ve said already, we know that 1.3 multiplied by our missing number gives us an answer of 3.9. Now, if we look at the tenths digit, what do we multiply three by to give us nine-tenths? Well, we know three times three is nine. And so, three-tenths times three is nine-tenths.

Perhaps our missing number might be three. Let’s write it in and see whether this gives us the answer 3.9. As we’ve said already, three lots of three is nine. And then, if we move to the ones column, one times three is three. We were right. 1.3 times three is 3.9. Our multiplier, our first missing number, is three. All the numbers in the top row are being multiplied by three to give us the numbers in the bottom row.

Now, we can apply this information to help us find the second missing number. We need to multiply 3.5 by three to find out what it is. Let’s use the same written method as we did with the last calculation. 3.5 — this time we know what we’re multiplying by, and it’s going to be three. And before we start, let’s make sure we include a decimal point in the right place in the equal sign. This way, our digits are going to have the correct value.

First, we’ll multiply the tenths. Five-tenths times three equals fifteen-tenths because five times three is 15. Fifteen-tenths is the same as five-tenths and we can exchange ten-tenths for one whole. Into the ones column, three times three, as we’ve said already, is nine. And we’ve also exchanged one, so that makes 10, 10.5. We multiplied 3.5 by the multiplier, which was three, to give us our second missing number, 10.5. Our two missing numbers in the table from left to right are three and 10.5.

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