What is full of holes but still holds water?

You have two buckets of 11 liters and 6 litres.
How can you measure exactly 8 litres?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

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

There are three identical triplets sisters. Demi is the oldest of them all and she always speaks the truth. Diana is the next one who is a liar always. Drew, the youngest of them all speaks both truth and lies randomly.

On a rainy day, a family friend Victor visited them. Since there were starkly identical, he was not able to recognize them. Thus to clarify, he asked one question to each one of them.

He started with the one standing on the left and asked, 'Which sister is in the middle of you three?' She answered, 'That's Demi.'

Then, he asked the one standing in the middle, 'What is your name?' She answered, 'I am Drew.'

Finally, he asked the one standing on the right, 'Who is standing in the middle?' She answered, 'She is Diana.'

Victor was left baffled. He asked the questions three times and received different answers every time.

Can you tell who was who?

Only Highly Attentive Can Spot The Ladder In This Library In 7 Seconds! Can You?

Prove that twice of ten is the same as twice of eleven.

A pond had 60 fish, out of which, all but 20 died.
How many fishes are now present in that pond?

Sherlock Holmes was challenged to make a pre-drawn line smaller without erasing it. He did it in fractions of seconds. How?

Find the missing number: 1, 2, 3, 10, 10, ?, 9,802