Which number should replace the question mark?

You need to remove two matchsticks to make the below equation true. Can you do it ?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?

Something Extraordinary happened on May 6th 19778 at 12:34am what was that?

You walk into a room that contains a match, a kerosene lamp, a candle and a fireplace. What would you light first?

They do not possess flesh or feathers or scales or bone
But still, they are blessed with fingers and thumbs of their own.

What always comes into a house through the keyhole?

Why do we preferably have round manhole covers and not square ones?

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?