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

Which of the following words don't belong in the group and why?
CORSET, COSTER, SECTOR, ESCORT, COURTS

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?

Seven Robbers robbed a bank and hide the coins in a lonely place.
They decide to divide the money equally the next morning. Two greedy robbers decided to cheat the others and reach the place at night. They equally divided the coins between them, one coin left. So they called another robber and then they decided to divide equally among the three. Sadly again one coin left. The same thing happened to the 4th 5th and the 6th robber.
However, when the 7th robber reached in the morning, they can divide the coins equally.

How many coins were there in total?

How can one talk without saying a single word?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

What does the below mathematical rebus mean?

Which flower has two lips?

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

Akbar called Birbal and asked him to draw a line on the floor. He asked Birbal to make that line smaller without erasing it. Birbal smiled and did it before Akbar could blink his eyes.

How did he managed to do it?