We appreciate your service.

My wife, father-in-law and I were playing a board game with my brother-in-law. In this game, we were playing as detectives who have to try to find his character, but each turn he could move in secret in one of several directions. We were a few turns in at one point and he could have been in any of dozens of places at this point. We drove him nuts by saying "he's either in this spot or he's not, it's a 50-50 chance." He kept arguing "I could be in a ton of places! It's not a 50-50 chance!" But we just kept pretending we didn't understand and arguing that there were only two possibilities, he's there or he's not, so it was clearly a 50-50 chance. He got quite angry.

Either I become president, or I don't.

Therefore, the odds of me becoming president is 50%

Brb committing 34 felonies.

The thing with that is that it's actually a useful generalization to make in a lot of scenarios.

If you know nothing about the distinction between two possible outcomes, treating them as equally likely is a helpful tool to continue with the back of the envelope guess. Knowing this path needs 5 coin tosses to go right and this one needs 10 is helpful to approximate which is better.

Your example is obviously outside the realm where you have zero information, so uniform distribution is no longer the reasonable default. But the idea is from a reasonable technique, taken to extremes by someone who doesn't fully get it.

On the other hand: Half of my lottery tickets were jackpots. I never played and have (1/2 * 0 = ) 0 jackpots.

Maybe I'm wrong but by writing "increase by 80%" there is ambiguity you don't get if you instead spelled out:

1. Increase by 80 percent
2. Increase by 80 percentage points

Or "by 80 percentage points"

i wish it was more common to also indicate the precedence of a percentage increase, so that it’s easier to know if i’m dealing with (x + y ) * z or x + (y * z). although that’s admittedly a lot harder to communicate.

The fact that it is even allowed in so-called civilized countries is outrageous. In the US it common because some religious nut was obsessed with children's masturbation.

×25% gives you 1/4 the original value, whereas +100% is double the original value, let's say 8/4 to keep it consistent. ×125% (in case a 1 is missing) is still only 5/4 the original value.

Is there a typo in your comment?

I'm quite willing to bet that 70% of the population has no clue that percentages, fractions, and decimals are the same thing.

Why not both?

I've always thought of math as a language and I talk to my kids about it that way too. Math is an other way to describe the world.

It's very different from spoken languages and translating between the two needs to be learned and practiced.

Our math education doesn't include enough word problems and it should be bi-directional. In addition to teaching students how to write equations based of sentences we should teach them how to describe what's going on in an equation.

10% of your people vote for a party.

The votes increase by 10% => now 11%

The votes increase by 200% => now 30%

The votes increased by 50 percent points => now 60%

The annoying part is that there is no well-known notation for showing percentage points, so people use % for both percentages and percentage points.

Exactly. Unfortunately, they aren't used widely and consistently enough. Even in the press. So you frequently have to second guess what you're reading.

Sleep deprived fraction lover: I had a 1% chance, and I doubled my chances. Now due to 1/100 * 1/100 I chances are 0.0001%.

What makes this “girl” math?

And then there was that bogus article that said Argentina had lowered it's inflation to 2% and you find out in the article that's monthly inflation and the yearly figure was like 190%.