Chetvertak is a word with several meanings. Dahl's Explanatory Dictionary says that it is a silver coin worth 25 kopecks, that is, a quarter of a ruble, and also cites many other meanings.
Quartet - how much?
The answer seems to be simple - it’s 25 cents, a quarter of a ruble. But Dahl does not stop there. A quarter, only rainbow or hundreds, could be called a bill in denominations of 25 rubles. This is also evidenced by the Dahl dictionary, which was compiled in the middle of the XIX century. So it was a bill of imperial times. And how much did this quarter cost in Soviet times? In those years, the word also denoted a paper bill of 25 rubles. Usually it was used in colloquial speech. Sometimes such a banknote was also called a quarter. Ten rubles was called a chervonets - from old memory, from pre-revolutionary times. Then it was a gold coin, and the name came, as you might guess, from pure gold - high-grade gold with a low copper content, giving a reddish ("red") tint. Five rubles in the Soviet years were called five-ruble, three - three-ruble note.
Currently, the word “quarter” can be considered obsolete, because at the moment, no coins or denominations of 25 kopecks or rubles are issued. Therefore, modern people ask the question of how much is a quarter.
The origin of the word and the variety of meanings
Depending on the context, a quarter may be a horse or a bull in the fourth year of life, and a plot of steppe land plowed for the fourth time. The word “quarter” is formed from the numeral quarter, and it is from the numeral four, which is why the spectrum of its meanings is so diverse. After all, a quarter is not only the ruble or hundreds! So how much is a quarter? So they can call it 25 years of life - also as if dividing a hundred years into four parts. Wherever the number 25 appears, a quarter is understood as a quarter of a hundred because in our decimal number system 100 is an important and symbolic number.
So, the answer to the question: “Quarter - how many rubles is it?” ambiguous and depends on the context: on the historical period, on whether it is a coin or a bill.