Qǐnɡwèn, zhè tiáo kùzi duōshǎo?
False: 请问，这条裤子多少？
Qǐnɡwèn, zhè tiáo kùzi duōshǎo qián?
True: 请问，这条裤子多少钱？
“多少”用来询问数量。这个句子是问裤子的数量，还是问裤子的价钱？要是问裤子的价格，在“多少”的后边要加上中心语“钱”。
多少 is for asking about quantity. But it is unclear here whether the sentence is a question about the number or a question about the cost of the trousers. Such a problem can be solved by putting the head word 钱 after 多少.
