What is the next number in this series?

4,12,84,3612....

What four weights can be used to balance from 1 to 30 pounds?

On a magical land of Mexico , all the animal in the land are rational.

There are 10 tigers and one goat.
Tiger can eat goat but since it's a magical land , the tiger who eats the goat , turns into goat and then can be eaten by the remaining tiger(s).

If we leave them for some time then how many goat and tiger will be there , when we come back ?

I have Rs.50 and I spend it in the way as below.

You bought me for dinner but never eat me. What am I?

I went to the bookshop and spent one-half of the money that was in my purse.

When I came out, I found that I had as many cents as I had dollars and half as many dollars as I had cents when I went in. Find the money in my purse when I entered the store.

A little girl goes to the store and buys one dozen eggs. As she is going home, all but three break. How many eggs are left unbroken?

A seven-year-old kid challenged his classmates that he can make the number one disappear by adding something to it.

How can he do that?

There is an English word that can be used up to four times in a row without modifying the spelling and form a valid grammatical sentence.

Do you know what word is that?

What does this rebus riddle means ?