Missing information: rate problems

0:00- [Instructor] We're told that Amaru bought five kilograms of apples and two kilograms of strawberries to make treats for a bake sale. What additional information is needed to find out how much one kilogram of strawberries cost? So before I even look at the choices, well, first of all, you should pause this video, try it on your own.

0:20But I'm not even gonna look at the choices and I'm just gonna try to answer the question straight without looking at it. So they're telling us how many kilograms of apples Amaru bought and how many kilograms of strawberries. What we want to, what we care about is how much does one kilogram of strawberries cost?

0:35Well, in order to figure out how much one kilogram of strawberries cost, we have to know how much did Amaru pay? So how much did the, how much did Amaru pay for the two kilograms of strawberries? If we know how much they paid for two kilograms, then we can divide by two and say, "Okay, that's how much it's going to be per kilogram."

0:53So for example, if Amaru spent say, $10, which they didn't tell us, I'm making that up, on two kilograms, then we know that this is the same thing as $5, $5 per one kilogram. But we don't have to actually figure out the actual amount per kilogram because they didn't give us enough information.

1:13But let's see which of these choices make sense based on what I just said. We need to know how much money Amaru spent on strawberries. Yep, that's exactly what I just said. So that is likely the right answer. But let's look at the other ones. We need to know how much money Amaru spent.

1:29The reason why that's not going to be so useful is they also spent money on apples. And so you don't know how much, if you just know the total amount Amaru spent, you don't know how much is on apples and how much is on strawberries. So I would rule that one out.

1:44No additional information is needed. No, we already know. If you just know that Amaru bought two kilograms of strawberries, but didn't know how much they spent on the strawberries, then you're in trouble. So we wanna rule that one out. We need to know how much money Amaru- How much money Amaru, this S shouldn't be there, spent on apples.

2:00Well, that's not, that would help figuring out how much apples cost per kilogram, but not, it will not help us how much, how much strawberries are per kilogram. Now if we knew B and D, then maybe we could figure out, we could back into that A, and then we could back into that the per kilogram cost.

2:17But just D by itself is also not going to be enough. And so we're done with that one. Let's do another example actually. So in this example, we're told Wendall spent $87 on amusement park tickets for himself and his friends. He also spent about $26 on bus tickets to get to the park.

2:39What additional information is needed to determine how much each amusement park ticket costs? So pause this video again and have a go at that. All right, so we just care about each amusement park ticket. So really this information on bus tickets is really not that useful for at least the question we're getting at.

2:55We know Wendall spent a total of $87 on amusement park tickets, but we don't know how many tickets he actually bought. It just says for himself and his friends, we don't know how many friends it might be two friends, it might be 20 friends that he bought tickets for.

3:12So what we need to figure out is how many total tickets did he buy? How many people did he buy tickets for, including himself. If we know that we just divide $87 by the number of tickets, and then you know how much each ticket costs. So let's see, we need to know the number of tickets bought.

3:27Yeah, that's right. I like that choice. We need to know the cost of each bus ticket. No, that's not what we're asking. And that would not help us with the amusement park tickets. Yeah, we definitely need additional information. We need to know the amount of money Wendall started with.

3:41No, that does not help us 'cause even if you knew that, you would maybe know how much Wendall ends up with after spending this money, but you will still will not know how much each ticket costs. So we would rule that one out as well.