Can anyone tell me a word in the English dictionary which has a silent 'z'?

You are in a room that has three switches and a closed door. The switches control three light bulbs on the other side of the door. Once you open the door, you may never touch the switches again. How can you definitively tell which switch is connected to each of the light bulbs?

Find the next number in the series?
2, 12, 36, 80, 150, 252, 392, _ ?

There are six people in a family namely M, N, O, P, Q and R.

R and O are brother and sister.

N is the brother of Q's husband.
P is the father of M and grandfather of R.

How many male members are in the family?

By using 'because' continuously three times, can you make an English statement ?

What mathematical symbol can be put between 5 and 9, to get a number bigger than 5 and smaller than 9?

If there are fifteen crows on a fence and the farmer shoots a third of them, how many crows are left?

What number should come in place of the question mark below?

If you toss a coin 10 times and it lands heads up every time, what are the chances it will land heads up if you toss it again?

In the image below, you can see two glasses and two matchsticks.You need to move four matchsticks in such a manner that the crosses come inside the glasses. Note: you cannot move the crossed.