During which month do people sleep the least?

Look at the below sequence of letters and tell us what the next letter should be:

O T T F F S S ?

Write the next letter in this sequence.
O, T, T, F, F, S, S, E, __
**Hint: It is a Number Series Puzzle

What's a single-digit number with no value?

In a mathematical quiz, you are asked the following question:

Use three 9s in a mathematical expression without dividing or multiplying to form the number one.

Can you answer the question?

I’m tall when I’m young, and I’m short when I’m old. What am I?

It walks on 4 when its young, walks on 2 when it's older, and walks on 3 when its very old?

What is more useful when it is broken?

We have shown you a regular water barrel as below. Without using any measuring device can you check if the barrel is more than half-filled or less than half-filled?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?