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One-step equations intuition example

Video transcript

Now you've got your chance to use this scale to figure out how much something weighs. So we're asked, how much does Old Spice Man weigh? We have Old Spice Man, this little guy here, plus you have 3 blocks. So on the left-hand side, you have Old Spice Man plus 3 blocks. And you see that the scale is balanced. On the right hand side, you have 8 blocks. So Old Spice Man plus 3 is equal to 8 blocks. And you can see what happens when we do something to one side of the scale or another. If we were to take a block from the right-hand side, all of a sudden, the right-hand side becomes lighter and it tilts up. And our scale is no longer balanced, and we can no longer say that the left and the right-hand side is equal. And there's an explanation of it below here. So what we want to do is add or remove blocks from the left or right-hand sides. So essentially we're just left with Old Spice Man on the left-hand side, but the scale is balanced. So whatever is on the right-hand side is how much he weighs in blocks. So let's see if we can do that. So let me add that block back. That's where we started from. So let's see, I want to get rid of these 3. So if I take 1 away from the left-hand side, well, I can't just do it there, because now, all of a sudden, the left-hand side is too light. So I'm going to have to take 1 away from the right-hand side as well. Well, let me do it again. Take 1 away from the left-hand side. We'll have to do 1 from the right-hand side as well. And I'm getting close-- 1 from the left-hand side, now 1 from the right-hand side. And it is a balanced. Old Spice Man is equal to 5 blocks. And you see what happened here algebraically. I took 1 from the left and right-hand side. I did it 3 times. So we started with essentially Old Spice Man, or you could call it x, plus 3. But then we ended up subtracting 3 from the left-hand side and subtracting 3 from the right-hand side. So we subtracted the same number from both sides to get the weight of Old Spice Man. And we could check it right over here. And very good.