While the majority of sample online citizenship test and United States practice citizenship test found online consist of normally 100 questions, the US Government official conducting the test will only resort to asking a few, anywhere between 10 to 25.
There are immigration services and immigration websites selling citizenship kits or even citizenship packets that are selling you the application and sample questions.
Some of these kits are available on eBay as well. These same questions are available for free all over the web and on the official US Immigration website.
You can find the same questions here on our site.
U.S. History and Gov. Questions