Question Video: Adding Multidigit Decimals | Nagwa Question Video: Adding Multidigit Decimals | Nagwa

Question Video: Adding Multidigit Decimals Mathematics

Find 657.2436 + 123.64532.

02:35

Video Transcript

Find 657.2436 plus 123.64532.

So to solve this problem, the most common way to do this would be using column addition, and we’re gonna have a look at that in a second. But also, if we saw this kind of problem and wanted to try and solve it mentally, there is a method we could use, because what we could do is first of all take a look at the 657 and the 123. Well, if we add three from the 123 to 657, we get 660. And then, if we add 120, which is what we have left of our 123, to 660, we get 780.

So now, all we need to do is add the decimal parts of our numbers, and we can do that using our place values. So, we’ve got tenths, hundredths, thousandths. And then, we’ve got ten thousandths for the first number and the second number we’ve got a hundred thousandths. So, if we look at the tenths, we’ve got two and six, which is eight. And then the hundredths, we’ve got four plus four, which is eight again. Then, we’re carrying this on for the other place values, and we’d have 892. We get the two because we’d have zero hundred thousandths in our first number and two hundred thousandths in our second number. And this will give us our answer, 780.88892.

Now I did mention that we’re also gonna show you how to do this with a more formal method, which is using column addition. So as with any decimal column subtraction or addition, the key is to line up the decimal points, which I’ve done here. But I’ve also added in a zero where we didn’t have a value in one of the place values in the first number, which is the hundred thousandths. And I’ve just done this just to avoid confusion.

So first of all, starting from the right-hand side, we have zero add two, which is two; then six add three, which is nine; then three add five, which is eight; four add four, which is eight again; then two add six, which is eight again. Then, we’ve got a decimal point, which is lined up. Then, we’ve got seven add three, which is 10. So we’ve put a zero in the units column, and then we carry one into the tens column. Then, we’ve got five add two add the one we carried, which gives us eight. And then finally, we’ve got six add one, which is seven. So therefore, we get the same answer. So we can say that 657.2436 plus 123.64532 is 780.88892.

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