Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Christina is practising her dance steps along with her friends. In a particular sequence, all of them form a row. At that point, Niharika is standing in the 4th position from either end of the row.
Can you find out how many girls are practising together?

If you're 8 feet away from a door and with each move you advance half the distance to the door. How many moves will it take to reach the door?

There are forty elephants and they have forty-fore heads. How can this be possible?

You are on your way to visit your Friend, who lives at the end of the hill. It is his birthday, and you want to give him the cakes you have made. Between your house and his house, you have to cross 5 bridges, and as it goes in the land of make believe, there is a troll under every bridge! Each troll, quite rightly, insists that you pay a troll toll. Before you can cross their bridge, you have to give them half of the cakes you are carrying, but as they are kind trolls, they each give you back a single cake. How many cakes do you have to leave home to make sure that you arrive at a friend's house with exactly two

Make the seating arrangement of 10 children in such a way that there are 5 rows with 4 children in each row.

10+10 and 11+11 can give you the same answer.

Explain how?

There are a number of books on a shelf. If one book is the 4th from the left and 6th from the right, how many books are on the shelf?

It belongs to you, but other people use it more than you do. What is it?

The pound is not a finish.

We are sharing a few instructions below, which you have to use in any suitable order to modify the above sentence such that the end sentence is a scientific fact.

- Eliminate a letter and supplement another in its place.
- Take away one word.
- Remove one letter from one word.
- Get rid of two letters from one word.
- Swap a word with its antonym.