Video: Understanding the Relation between Addition and Subtraction in Multidigit Numbers

Find the number added to 7334859 to give 8 million.

03:46

Video Transcript

Find the number added to 7334859 to give eight million.

Let’s imagine this blue space represents 7334859. The yellow space is eight million. The green space would be equal to the number we need to add to 7334859 to give us eight million. To find the missing space, we need to take the blue space away from eight million. We need to subtract 7334859 from eight million.

Eight million is an eight with six zeros behind it. We line up our units carefully and then we can subtract. When we look at our units place, we’re trying to take nine from zero. And that’s not going to work. We need to borrow. We can’t borrow from the tens place or the hundreds place or the thousands place or the ten thousands place or the hundred thousands place. We have to borrow from the millions.

So we take one away from our millions and then we have ten hundred thousands. We take one away from our hundred thousands. That gives us nine hundred thousands plus ten, ten thousands. If we take one away from our ten thousands, we will be left with nine ten thousands and ten one thousands.

Following that same process, we take one away from our thousands. That leaves us with nine thousands and ten hundreds. We do the same thing, take one away from our hundreds. That gives us nine hundreds and ten tens. And finally, we’ll take one away from our tens leaving us with nine tens and ten ones.

And now we can subtract. In the units place, it now says 10 minus nine which equals one. In the tens place, nine minus five equals four. In the hundreds place, nine minus eight equals one. In the thousands place, nine minus four equals five. In the ten thousands place, nine minus three equals six. Also in the hundred thousands place, nine minus three equals six. In the millions place, we have seven minus seven, which equals zero.

When we take 7334859 away from eight million, we get 665141. That is what you would add to 7334859 to give you eight million.

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