Comparison word problems: roly-polies | Addition and subtraction | 1st grade | Khan Academy

Leah has nine roly polies. Let's write that down. Leah has nine roly polies in her bug house; she has one more. She has one more than Dingan, is I think how I would say that name.

How many roly polies does Dingan have? So that's what we need to figure out. We need to figure out how many roly polies does Dingan have. So this right over here is our question mark.

Now, it's always good when you look at a word problem like this. You say, "Okay, well, Dingan have more or less than Leah?" Well, it says Leah has one more than Dingan. So Leah is going to have more, and how much more? One more.

So Dingan is going to have one less than Leah. If Leah has one more than Dingan, then Dingan has one less than Leah. So how do we write one less? Well, we could just subtract one. So this right over here, this is one less. One less. This is saying that Dingan has one less than Leah.

So how much does Dingan have? Well, he's going to have eight roly polies. Eight roly polies. Now, another way you could have done it, you could have drawn Leah's roly polies: 1, 2, 3, 4, 5, 6, 7, 8, and that would have been them rolled up. You said, "Okay, that's one more than Dingan," so Dingan has one less than this. So one less than this, you just take away one of these, and you're left with 1, 2, 3, 4, 5, 6, 7, 8. You're left with these right over there.

Let's do one more of these. Whoops! All right, let's do one more. So they tell us the mass of a small box is 7g less than the large box. The mass of the small box is 6g. So let's write that.

They tell us the small box—small, small box—it has a mass of 6g, and we need to figure out what is the mass of the large box. Large, large box—this is what we need to figure out. So this is a question mark.

Now, like we did in the last problem, is the large box going to have a larger mass or a smaller mass? And we shouldn't just look at the names of the box; we should look at what they tell us. They tell us that the mass of the small box is 7g less than the large box.

So this—the small box is 7g less than the large box—and that's another way of saying that the large box is 7g more than the small box. So another way to say 7g more than the small box is 6g plus 7g. That's 7g more; that's going to equal the mass of the large box.

So what's the mass of the large box? Well, 6 + 7 is 13. 6 + 7 is 13, and we're done.