Language Course From Wikibooks, the open-content textbooks collection Contents

Ich bin __ Jahre alt.
I am __ years old.
Du bist __ Jahre alt
. - 
You are __ years old.
And now the plural version of the 1st person...
Wie alt sind wir? - 
How old are we?
The responses you will get is...
Wir sind __ Jahre alt. = 
We are __ years old.
Ihr seid __ Jahre alt. - 
You all are __ years old.
To ask this important question in the 2nd person. First, we will learn the biggest question here, "
How 
old are you?
" which is...
Wie alt bist du? - 
How old are you?

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And there is only one response to this it is...
Ich bin __ Jahre alt. - 
I am __ years old.
For the equally important plural 2nd person...
Wie alt seid ihr? - 
How old are you all?
Which the response is...
Wir sind __ Jahre alt. - 
We are __ years old.
And formal question, for both singular and plural is...
Wie alt sind Sie? - 
How old are you?
How old are you all?
You should all ready get the pattern for this, but we are going to keep on doing this doing this list, if 
you aren't sure of something or you are confused. So for the 3rd person...
Wie alt ist er/sie? - 
How old is he/she?
The responses to this are...
Er ist __ Jahre alt. - 
He is __ years old.
Sie ist __ Jahre alt. - 
She is __ years old.
And now the plural 3rd person of question and response...
Wie alt sind sie? - 
How old are they?
And of course the response...
Sie sind __ Jahre alt. - 
They __ years old.

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Now with some people you might be able to guess their age, and you could ask them directly about it. 
This is usually pretty of rude, but it illustrates nicely how the phrase has to be changed if you ask a yes-
no-question, so let's get started, anyway!