Replace the question mark with the correct number.

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

Which flower has two lips?

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?

What is in seasons, seconds, centuries and minutes but not in decades, years or days?

When it's bad luck to meet a black cat?

A man has eighty-one cows ( numbered 1,2,3...81 as such). The beauty is that cow no. 1 gives 1ltr of milk, cow no. 2 gives 2ltrs of milk and so on. The man wants to equally distribute the cows among his nine sons so that each one of them gets the same quantity of milk.

What Does this text mean:

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There’s a one-story house in which everything is yellow. Yellow walls, yellow doors, yellow furniture. What colour are the stairs?

Can you name four days which start with the letter 'T'?