"A quarter of a million" is correct and natural. "A fourth of a million" is strange, but would be understood. The only way I know to say "0.3 million" is "oh point three million." Depending on how precise you want to be, you could say "about a third of a million."

"Two hundred fifty thousand" is much more common than "a quarter million." Your second number is "three hundred thousand."

Good answers here. In American English we sometimes say 'k' in place of a thousand. So you can say 'quarter million' but you can also say 250k. In my experience 'k's use to represent one thousand in speech has almost exclusively been when talking about money but I believe it can be used appropriately for any measure in thousands, when writing. For example, I might write 100k miles but I would say 'One hundred thousand miles'. But if you asked me to quote you a price on a car I would say 'Fifty k' meaning $50,000. I could be wrong but I cannot recall anyone saying 'k' when speaking of anything but money.

It depends what you are emphasising whether you talk about hundreds of thousands, or about millions. Another option is to say “point 3 million.” Point means the decimal point in 0.3

Hello, lphlch. Good question! These are the expressions you would use: 0.25 million = a quarter of a million 0.3 million = a third of a million For example, the city spent a quarter of a million dollars on building the new park and lost a third of a million dollars due to crime.