If eleven plus two equals one, what does nine plus five equal?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

What is the below Rebus indicate?

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 does this Rebus Picture mean?

You have two rectangular wires.

Both of them have property that when you light the fire from one end , it will take 60 minutes to get completely burn.

However, they do not burn at consistent speed (i.e it might be possible 1st 20% burn in 50 minutes and 80% can burn in 10 minutes).

So how could you measure 45 minutes ?

A sundial has the fewest moving parts of any timepiece. Which has the most?

One absent-minded ancient philosopher forgot to wind up his only clock in the house. He had no radio, TV, telephone, internet, or any other means for telling time. So he travelled on foot to his friend's place a few miles down the straight desert road. He stayed at his friend's house for the night and when he came back home, he knew how to set his clock. How did he know?

There is one four-digit whole number n, such that the last four digits of n2 are the original number n

Can you place three balls such that the equation shown in the picture holds true?