Can you find the missing piece of the Porsche?

If 21x = 79x, what is the value of x?

I sleep during the day and fly at night, but I have no feathers to aid my flight. What am I?

Prove that twice of ten is the same as twice of eleven.

What is next number in the pattern below:

131 517 192 123 ?

What has many teeth, but cannot bite?

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 ?

There is a place where if I stand up straight, I will still be considered sideways.

There are three light switches outside a room. One of the switches is connected to a light bulb inside the room.
Each of the three switches can be either 'ON' or 'OFF'.

You are allowed to set each switch the way you want it and then enter the room(note: you can enter the room only once)

Your task is to then determine which switch controls the bulb?

Why 1729 is a magic number? Answer Logically.