Replace the question mark with the correct number below.

A frog is at the bottom of a 30-meter well. Each day he summons enough energy for one 3-meter leap up the well. Exhausted, he then hangs there for the rest of the day. At night, while he is asleep, he slips 2 meters backwards. How many days does it take him to escape from the well?

Rectify the following equality 101 - 102 = 1 by moving just one digit.

I am lying and I always lie. Tell me whether I am lying or telling the truth.

Before the start of the car race, John and Jacob have the same amount of fuel in their car. With this fuel, John can drive for 4 hours while Jacob can drive five hours.
After a time they realize that the amount of fuel left in John's car is 1/4th of the fuel in Jacob's.

For how long they are racing?

Can you identify the direction in which this bus is moving; left or right?

Hint: The bus is moving on the roads of London.

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

In front of you, there are 9 coins. They all look absolutely identical, but one of the coins is fake. However, you know that the fake coin is lighter than the rest, and in front of you is a balance scale. What is the least number of weightings you can use to find the counterfeit coin?

I inserted a coin in a bottle and closed its mouth with the help of a cork. Now, I was able to take the coin out from the bottle without taking out the cork or breaking the bottle. Can you tell me how I did it?

Always in you, Sometimes on you;

If I surround you, I can kill you.

What am I?