I am white when I am dirty, and black when I am clean. What am I?

I am working in a bus company. The company recently went under expansion and therefore there was not enough room for all the buses. As a result, twelve buses had to be stored outside.

If the company decides to expand the garage space by forty percent, enough space to accommodate the current buses will be created leaving enough space for twelve more buses if the need arises in future.

Can you calculate the number of buses that the company owns at present?

There were five men at church, and it started raining while they were outside. The four that ran still got wet, but the one that was still stayed completely dry. Why did he stay dry?

What does the below rebus puzzle mean?

Can you find out which triangle will have a bigger area among the following?
1. A triangle with sides 300, 400 and 500
2. A triangle with sides 300, 400 and 700

No one wants to have it, but if one got it, he does not want to lose it. What is It?

In the below-given picture of a pretty girl, there is something wrong. Can you find out what it is?

What is the probability of getting five Mondays in a 31-day month?

If it took eight men ten hours to build a wall, how long would it take four men to build it?

The sum of a mother, her baby and her dog's weight is 170 Kg. How much does the baby weigh if the mother weighs 100 kg more than the combined weight of the baby and the dog, and the dog weighs 60 per cent less than the baby?