Mei puzzles over this. How are they going to be graded? Are they going to fail if they don't somehow guess the right number with no information? Are they supposed to go to the library and do research on the size of the sun? How could it possibly grade them on whether their guess felt right? Do they lose any points if they just make up random numbers and write them down? It feels pointless to ask any of this out loud because it's not like anyone else knows how they're being graded. 

Mei looks down at her assignment sheet angrily.

"Fine. 'Question one: Estimate how many liters are in a barrel of oil and how many barrels of oil China imports every year.' A barrel of oil is like, a meter tall and half a meter across. So that's, what, a quarter of a cubic meter? So if there's a thousand liters of oil in a cubic meter then there's a quarter of that in a barrel. And there's, I don't know, a billion people in China? So if everyone gets a barrel a year then that's 250 billion liters of oil. I have no idea how right that's supposed to feel! I'm pretty sure it's wrong! But it's probably less wrong than, like, '5'??"

Mei has no idea if she's doing too much math or not enough and this is not the sort of thing that one is normally uncertain about in a math class!

"...that does sound a lot less wrong than five but that's not how I'd do it, the way I'd do it is that China is the biggest importer of oil in the world so it has to be a lot, like, on the order of millions of barrels a lot, except I think oil is usually measured in barrels per day so actually it's a couple orders of magnitude more than that?" 

"I guess probably people use more than a barrel of oil a year. Oil is used for lots of things."

"Yeah. So if China has a billion people, I think it has a more than that but I don't know how much more and that sounds right, and they each use five barrels of oil a year on average, then that would be about five billion barrels a year? Which sounds at least not obviously wrong for a big country with a lot of factories?" 

"If somebody who knew anything about the topic told me that number I would totally believe them. And I don't see how we could get a better guess without more information, so..."

Mei writes down "250 liters" and "5 billion barrels" next to question one and grumpily contemplates the vastness of the sun.

Kinsei does the same. 

"For the Earth I'm tempted to put that it's one earth-mass, that's a real unit of measurement, they use it for planets? It doesn't say you have to give the answer in kilograms. But that doesn't tell us how much smaller it is than the sun since I don't remember how much an earth-mass is." 

"I really don't see how we're supposed to guess this at all. There's nothing to go on! The Earth is big and the sun is even bigger by some totally mysterious amount. It's not like you can picture them side by side and go 'ah yes the sun is so many Earths across'!"

"...well, it says the sun is 2 with thirty zeroes kilograms, so we know we're working with the kind of scale where it's easier to say that things have thirty zeroes than to write out all the zeroes they have?" 

"Great, so the Earth has fewer than 30 zeroes and more than 3 zeroes. Uggh I think I remember hearing once how many Earths you can fit in the sun but I can't remember how many it was! A hundred sounds too small and a million sounds too big?"

"The Chinese boy who was speaking English said it was a million earlier, but that's volume not mass so it doesn't help us very much...

...wait actually yes it does, it means we know the ratio has to be less than a million?" 

"Can we not just count the number of zeroes in a million and take them away from thirty and go with that?"

"...yeah, we can probably do that? A million is one times ten to the seventh so that'd be... two times ten to the twenty-third? If it had exactly one millionth the mass of the sun? Except we know it has more because the earth is denser so I'm going to call it two times ten to the twenty-fourth." 

Mei writes down two times ten to the twenty-fourth. "Great, that's two questions done."

She looks at the rest of the worksheet and groans.