Early math review
Sal solves word problems comparing 2 numbers. Numbers in the problems are less than 10.
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- What is a roly-polie?(37 votes)
- Yes, and to add to the answer of OmniHex, they're also known as pill bugs, more specifically, Armadillidiidae. Some may have seen a different kind of roly-poly, known as the pill millipede. They have the ability to conglobulate, (roll into a ball) which is a similar trait shared between the two.
- [Instructor] Lea has nine roly-polies. Let's write that down. Lea has nine roly-polies in her bug house. She has one more than Dingane, is I think how I would say that name. How many roly-polies does Dingane have? Dingane have. So that's what we need to figure out. So we need to figure out how many roly-polies does Dingane 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 will Dingane have more or less than Lea? Well it says she, Lea, has one more than Dingane. So Lea is going to have more, and how much more? One more, so Dingane is going to have one less than Lea. If Lea has one more, then Dingane has one less than Lea. 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 Dingane has one less than Lea. So how much does Dingane have? Well he's going to have eight roly-polies. Eighth roly-polies. Now another way you could have done it, you could have drawn Lea's roly-polies. One, two, three, four, five, six, seven, eight, nine, and that would have been them rolled up, and you said okay that's one more than Dingane. So Dingane has one less than this. So one less than this. You just take away one of these and you're left with one, two, three, four, five, six, seven eight. You're left with these right over there. Let's do one more of these, woops. All right, let's do one more. So they tell us the mass of a small box is seven grams less than the large box. The mass of the small box is six grams. So let's write that. They tell us the small box, small box, it has a mass of six grams. And we need to figure out what is the mass of the large box. 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 a large box gonna 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 seven grams less than the large box. So this, the small box is seven grams less than the large box. And that's another way of saying that the large box is seven grams more than the small box. So another way to say seven grams more, the small box is six grams plus seven grams. That's seven grams more. That's going to equal the mass of the large box. So what's the mass of the large box? Well six plus seven is 13. Six plus seven is 13, and we're done.