1. 斤 (jīn) is a common unit of measurement for weight in China. It is equivalent to half a kilogram, so 两斤 (two jin) is 1kg.
2. To ask about the price, we use the phrase 多少钱 (duōshao qián)?
To answer, we use the following words: ……块 (… kuài).
“Kuài” stands for “yuan”, so 3¥ is “三块” and 2¥ is “两块”.
“Kuài” is used in spoken Chinese. In written form, you will see the character 元, which reads as yuán. Also, note that “kuài” technically is a measure word (sometimes people will say the full phrase “块钱”, for example, 三块钱. Therefore, for 2¥ we say 两块 rather than 二块.)
Smaller units of the currency, unlike in English, are usually counted not in 1/100 of a yuan, but in “máo” (1/10 of a yuan): ……块……(毛)
So 3.40¥ is „three kuai 4 mao“ and 2.5¥ is “two kuai five mao”. Good news is that the word “mao” is usually omitted, so all you need to remember is that the units you are using are 1/10 of a yuan, not 1/100.
So 3.40¥ in Chinese is “三块四” and 2.5¥ is “两块五”.
1/100 of a yuan does exist and it is called “fen”. However, it is such a small unit that it is not used on a daily basis. Still, it is possible that you will see fen somewhere. To express a price with fen, we would use the following construction: ……块……毛……, e.g. 3.45¥ is …“三块四毛五”