What is the next number in this matchsticks series riddle?

Eight of us go fourth, not back, to protect our king from an attack. What are we?

You may enter, but you may not come in. I have space, but no room. I have keys, but open no lock. What am I?

What is always in front of you but can’t be seen?

A boy purchased a book from a bookkeeper and gave him $100.
The cost of the book is $50 but the bookkeeper has no change, so he gets the change from the next shop and returns the boy his $50.

After some time the next shopkeeper came with the $100 note and told the bookkeeper that the note was a fraud, so he took the money back.

How much loss did the bookkeeper face?

Can you find out the smallest number that can be conveyed as the sum of three squares in three unique ways?

What Time Should the last watch show in the below figure?

Can you find out which options fits best with the missing column?

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

The average age of 10 members of a committee is the same as it was 4 years ago, because an old member has been replaced by a young member. Find how much younger is the new member ?