What happened when the wheel was invented?

Can you calculate the probability of getting a sum of six when a dice is thrown twice?

I am not a bull but I have horns.
I am not an ass but I have a pack saddle.
Wherever I go, I leave silver behind me.

Who am I?

What is so fragile that saying its name breaks it?

Find the combined weight of the Cat, Dog and Rabbit in the given picture.

Decode the below four famous ciphers:

8P of the SS
1M of the E
1S of the SS
60M in 1H

Which Travels Faster? Solve below famous picture riddle:

On one occasion, A Boy collects 71 rupees in form of 20 paise and 25 paise. He collects a total of 324 coins.

Can you tell me how many 20-paisa and 25-paisa he got?

You have two buckets - one holds exactly 5 gallons and the other 3 gallons. How can you measure 4 gallons of water into the 5 gallon bucket?

(Assume you have an unlimited supply of water and that there are no measurement markings of any kind on the buckets.)

In The 1st month of this year(the year 2013), I noticed that the date 13-1-13 (13 January 2013) is special.

This date is special as:

Date * Month = Year.

Can you figure out which year of this century has a maximum number of such dates?