Video: KS2-M17 • Paper 1 • Question 21

9 − 3.45 = _.


Video Transcript

Nine subtract 3.45 equals what?

We can use column subtraction to help us find the answer. It’s important to remember to set out the numbers in the correct columns. Nine is nine ones, no tenths, and no hundredths. We need to subtract 3.45, which is three ones, four tenths, and five hundredths.

We start by subtracting in the hundredths column. There are no hundredths to take away the five hundredths from. And in the tenths column, there are no tenths for us to borrow from. So we have to move over into the ones column. If we borrow one from this column, we’ll be left with eight ones.

Now we have 10 tenths in the tenths column. And we can borrow one and add it to the hundredths column. Now we have 10 hundredths and we need to take away five, which is five. In the tenths column, we have nine subtract four, which is also five. And in the ones column, we have eight subtract three, which is also five. So we calculated that nine take away 3.45 equals 5.55.

We can check our answer is correct using the inverse operation by adding 3.45 and 5.55 to check we get nine. We start by adding in the hundredths column. Five plus five equals 10. We can write the zero and we need to carry the one into the tenths column. We need to add four plus five plus the one we carried, which makes 10. We can write the zero in the tenths column and carry the one into the ones column. Now we need to add three and five, which makes eight, plus the one we carried, which makes nine.

3.45 plus 5.55 equals nine. Nine take away 3.45 equals 5.55. We calculated our answer using column subtraction. And we checked our answer using the inverse, adding 3.45 and 5.55, to give us our original number of nine.

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