how many的用法：
对数量进行提问，many后面跟可数名词复数。
How many pandas are there?
那里有多少只熊猫?
How many lions can you see?
你能看到多少只狮子?
对therebe句型中主语的数量如:some,five,onlyone等提问时,如果主语是可数名词,不管主语是单数还是复数一般都用复数形式提问。
因为问话人不知道具体的数量是多少,而且many只能接可数名词复数形式,所以be一定要用are.即用Howmany+可数名词复数+arethere+地点/时间状语的句型结构。例如:
1、There is a book on the desk. (用how many改为特殊疑句)How many books are there on the desk 翻译：有多少本书在桌子上？
2、There are seven days in a week. (对划线部分进行提问)How many days are there in a week 翻译：一周有多少天？