Find the Next Number in the Sequence

2 9 3 1 8 4 3 6 5 7 ?

Can you find out the missing number?

? 4 5 3 5

9 5 7 10 3

Take one out and scratch my head, I am now black but once was red. What am I?

A man desired to get into his work building, however he had forgotten his code.
However, he did recollect five pieces of information
* Fifth number + Third number = 14
* The fourth number is one more than the second number.
* The first number is one less than twice the second number.
* The second number and the third number equals 10.
* The sum of all five numbers is 30.

What is the code ?

A landlord calls both of his sons and tells them that their horses will now decide who will transfer the inheritance. He tells them to race along the land till the end and the one whose horse will be slower will win and be the heir to all the property.

Both of them keep wandering for days but to no result. Then they ask a wise man regarding it. The man advises them on the matter after which they jump on the horses and race as fast as they can till the end. Why did they do it?

What did the wise man say?

How many letters are in the alphabet?

The square root of number 121 is "11". What is the square root of the number "12345678987654321."?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

What is in seasons, seconds, centuries and minutes but not in decades, years or days?