# Video: KS2-M16 • Paper 1 • Question 16

15.98 + 26.314 = ＿.

05:31

### Video Transcript

15.98 plus 26.314 equals what?

There are lots of different digits in these numbers. They both have a different amounts of digits and different number of decimal places. So rather than try to juggle all those digits in our heads, we can use column addition to find the answer. It’s really important that we line up the digits so that they’re in the correct columns. A good way to do this is to make sure that we draw the decimal points before we start.

Let’s start with the larger number. It won’t change the total at all, 26.314 plus 15.98. We can see that our second number doesn’t have anything in their thousandths column. We don’t have to, but just to make things neater, we can write a zero as a placeholder. Something that’s easy to forget and something that would really affect our answer is a decimal point. So let’s put that in before we start, make sure it lines up with the other decimal points. This will mean that all of our digits will be in the correct columns.

Start by adding the thousandths. Four thousandths plus zero thousandths equals four thousandths. One hundredth plus eight hundredths equals nine hundredths. Three tenths plus nine tenths equals 12 tenths. We know that 10 tenths make one whole. So this is the same as saying one whole and two tenths. So we can write a two in our tenths column and then exchange 10 of those tenths for one one or one whole.

Let’s add the digits now that have a whole value to the left of the decimal point. Six ones plus five ones equals 11 ones. Don’t forget we’ve got one one underneath. That makes 12 ones. So we can write a two in the ones place and exchange 10 of those ones for one 10. Finally, we can add the digits in the tens column. Two tens plus one ten equals three tens. And don’t forget the one underneath, four tens, 42.294.

This was quite a quick and efficient way that we could find the answer. But there is another method that we could use. What do we notice about the number 15.98 that might make it easy to add? Well, the number 15.98 is only two hundredths away from 16. A nice whole number that we could add very quickly. What if we started with 26.314 but then added 16 instead? And then, of course, we’d have to adjust the answer to make up for it.