Video: KS2-M19 • Paper 1 • Question 6

5.87 + 3.123 = _.

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Video Transcript

5.87 plus 3.123 equals what.

This problem asks us to find the total of a number with two decimal places and a number with three decimal places. Because both numbers have a different number of decimal places, it might make sense to use column addition to find the answer. That way, we can keep track of what each digit is worth.

The way to make sure that the numbers are lined up correctly is to put the decimal points level with each other. That way, each digit is in the correct column. Now, we can add each column the way that we’d add two whole numbers. But before we start, let’s put a decimal point underneath the other two decimal points so that our answer is a decimal too. If we forget that, our answer will be wrong.

First, let’s add the thousandths column. We can see that the first number only has two decimal places. So it doesn’t have any thousandths. If it helps us understand this, we can actually write a zero in the thousandths place. And the value of the number doesn’t change at all.

Zero thousandths plus three thousandths equals three thousandths. Seven hundredths plus two hundredths equals nine hundredths. Eight-tenths plus one-tenth equals nine-tenths. And finally, five ones plus three ones gives us eight ones. So to help us keep track of all the digits, we used column addition to find the answer.

5.87 plus 3.123 equals 8.993.

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