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

The person who makes it has no need for it. He who purchases it does not use it. The person who does use it does not know they are. What is it?

I am five letter word that is under you.
If you remove my 1st letter, then I am over you.
If you remove my 1st and 2nd letters then I am all around you.

Who am I?

Solve the equation by replacing the alphabet with numbers.

MOM + MOM + NO = BOOK=

What's the only room from which no one can enter or leave

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

A bank customer had $100 in his account. He then made 6 withdrawals. He kept a record of these withdrawals, and the balance remaining in the account, as follows:

Withdrawals Balance left
$50 $50
$25 $25
$10 $15
$8 $7
$5 $2
$2 $0
----- -----
$100 $99

Why are the Totals not tallying?

John, a 5-year-old boy, was really fond of the chocolates. He asked his Mother to give him some money to buy his favourite chocolates. His Mother gave him $45. He went to the shopkeeper and asked, "How much is one chocolate for?". The shopkeeper said $3 for one chocolate. Also, if you give me the wrappers of three chocolates, I will give you one for the exchange.
In total, how much chocolate could John eat?

You see a boat filled with people, yet there isn’t a single person on board. How is that possible?

What 4-letter word can be written forward, backward or upside down, and can still be read from left to right?