How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

Can you think of any three-dimensional shape that comprises of exactly two surfaces?

Can you count the number of triangles in the picture below?

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?

Count the number of triangles in the below picture?

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

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

It has five wheels, though often think four, You cannot use it without that one more, You can put things in it, you can strap things on top, You can't find it in the market, but you can still go shop. What is it?

Assume there are approximately 5,000,000,000 (5 billion) people on Earth. What would you estimate to be the result, if you multiply together the number of fingers on every person's left hand? (For the purposes of this exercise, thumbs count as fingers, for five fingers per hand.) If you cannot estimate the number then try to guess how long the number would be.

The chance of Mr John winning the lottery is 10%. All participants lined up and Mr John is 4th in the row. The first three participants lose the lottery.

What is the chance of Mr John now?