Possible instruction error in Basic math in JavaScript Guide?

[iamvictati]

Hi,

I'm quite new at this and currently completing TOP so I apologize for my ignorance or perhaps boldness (lol) but I came across an instruction in the Active learning: sizing a canvas box section that seems a bit mathematically weird for me.

Link: Editable Canvas Example

Exercise 3 says:

"Change the line that calculates x so the box is 250px wide, but the 250 is calculated using two numbers and the remainder (modulo) operator."

// Edit the two lines below here ONLY
x = 50;
y = 50;

ctx.fillStyle = 'green';
ctx.fillRect(10, 10, x, y);

How exactly is one supposed to calculate a total remainder of exactly 250px using % and only 2 numbers? Or was this instruction meant to say “division operator”? A division seems to make more sense, given that it's simple JS math.

Once again, apologies if I'm overstepping (lol) but I wasn't able to let it go and the only simple solution I found was to state const boxWidth = 250 + remainder which isn't part of the code given in the example.

[Josh-Cena]

You can calculate 50 using 43 and 7 using +. Surely you can create an expression that produces 250 using two numbers and %?

[iamvictati]

Thanks for your reply Josh. Could you please give the math expression? Math isn't really my thing and I can't find the answer with simple mental math.

[Josh-Cena]

Sure. Your goal is to find a and b such that a % b = 250. In other words, a = b * c + 250, where b is something larger than 250 (so it can allow a remainder of 250). Therefore one easy solution is to pick b = 251 and c = 1, then you would have a = 251 + 250 = 501. Verify: 501 % 251 === 250.

[iamvictati]

Thank you, Josh!!! :)))

The relief! I asked the AI for help and it gave me crazy answers with more complex math formulas and I couldn't let it go haha. Thanks for the save!

I think the exercise should use a simple division though for learning’s sake. I couldn't figure out the math by myself.

Either way, you are a saviour I really appreciate it! ^.^

[Josh-Cena]

No problem! I wouldn't trust AI on math-related stuff. In the future, if you have problems with MDN content, you can also ask in our Discord server, where it's hopefully more discoverable.

[iamvictati]

Ok, I'll keep that in mind and already joined the server. :)))