What happened when the wheel was invented?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

There are are five things wrong with this sentence; only geniuses will be able to to spot all of the mitstakes

How many words can a pen with half refill write?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

Jack was having a candle light dinner with his girlfriend. Suddenly a cold gush of wind entered through the open window and three of the ten candles were extinguished. Assuming that none of the other candles were extinguished.

How many candles are they left with in the end ?

If two fifty-foot ropes are suspended from a forty-foot ceiling that is twenty feet apart, how much rope will you be able to steal if you have a knife?

What has six faces, but does not wear makeup, has twenty-one eyes, but cannot see?

I am under you when I am whole.
I shift above you if you remove the first letter.
I come all around you if you remove the second as well.

Can you tell me who I am?

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?