Video: Adding Decimals to Mixed Numbers

Calculate 18.884 + (67 1/10).

02:39

Video Transcript

Calculate 18.884 plus 67 and one-tenth.

In this addition, we’re being asked to add a decimal and a mixed number together. Now, to make it easier to add these two different types of numbers, we could try converting 67 and one-tenth into a decimal. 67 and one-tenth is fairly easy to turn into a decimal. We simply write 67, and we write a one in the tenths column. 67 and one-tenth is the same as 67.1. And so, our addition has become 18.884 plus 67.1. We can add these two decimals together now using column addition.

Now, we can see that 18.884 has more decimal places than 67.1. And so, it’s important that we line up our numbers correctly. A good way to do this is to make sure that we align the decimal points of both numbers. And then we know that each digit has the correct value. And to make sure that our answer is correct, we could always put a decimal point in before we start as well. Again, making sure that it’s aligned with the other two decimal points. This way, we know the decimal point is in the correct place in our answer. This is something that can be easy to forget. So it’s a good habit to get into to put it in there before we start. Now, we can start adding from right to left as we would do with any other column addition.

Now, we can see that in our second number, there aren’t any hundredths or thousandths. So it might be helpful if we just put zeros in there as placeholders. Four thousandths plus zero thousandths equal four thousandths. Eight hundredths plus zero hundredths equals eight hundredths. Eight tenths plus one more tenth equals nine tenths. Eight plus seven equals 15. And one 10 plus six 10s plus the one 10 that we’ve exchanged equals eight 10s.

We managed to add the decimal and the mixed number together by first converting the mixed number into a decimal. So we then have two decimals to add together. By using column addition, we found the answer. 18.884 plus 67 and one-tenth equals 85.984.

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