Most of us know that if you search "10 + 2" Google will return the result "10 + 2 = 12" along with other search results. This is not limited to calculators, actually there are a lot of quick answers that we can get with Google search.
List of all such can be found at - http://www.google.com/landing/searchtips/
I will enlist most useful of them.
1. Weather - Weather Cityname
2. Time - Time Cityname
3. Word Meaning - Define Word
4. Currency - Put the currency to be converted like 10 USD in INR
5. Weight / Measurement - Search for the conversion like 10 pound in kilo or 10 meters in inches
Even Google suggest to search fill in the blank type of search like "Mahatma Gandhi was born in *" and you may see the answer on top few results. This one is also worth giving a try.
