Foreigners often make some strange mistakes in Chinese when they study the most difficult language--- ---Chinese. We try to analyze typical sentences to correct these errors.

         Chánɡjiānɡ bǐ Huánɡhé duōshǎo chánɡ ɡōnɡlǐ?
False: 长江比黄河多少长公里?
        Chánɡjiānɡ bǐ Huánɡhé chánɡ duōshǎo ɡōnɡlǐ?
True: 长江比黄河长多少公里?

“多少”不能放在谓语之前作状语。通常跟在名词或名词和量词前,作定语。“多少”应移到“公里”的前边。
多少 normally premodifies a noun or a combination of a noun and a measure word. It can not stay in front of the predicate to serve as an adverbial adjunct. We shift it to the position before 公里.