81 x 9 = 801. What must you do to make the this equation true?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

If in a code language, DISTANCE is written as IDTUBECN and DOCUMENT is written as ODDVNTNE, the how will THURSDAY be coded as in the same language?

I inserted a coin in a bottle and closed its mouth with the help of a cork. Now, I was able to take the coin out from the bottle without taking out the cork or breaking the bottle. Can you tell me how I did it?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

What will you call your mother's brother's brother-in-law?

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

What has one letter and starts with an E?

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?

I have cities, but no houses. I have mountains, but no trees. I have water, but no fish. What am I?