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

There are 100 bulbs in a room. 100 strangers have been accumulated in the adjacent room. The first one goes and lights up every bulb. The second one goes and switches off all the even-numbered bulbs - second, fourth, sixth... and so on. The third one goes and reverses the current position of every third bulb (third, sixth, ninth? and so on.) i.e. if the bulb is lit, he switches it off and if the bulb is off, he switches it on. All the 100 strangers progress similarly.

After the last person has done what he wanted, which bulbs will be lit and which ones will be switched off?

I am written with two letters.
I said with the one.
I usually am seen with the two.

Who am I?

I am quite hot but become too cold if you remove the first two letters. What am I?

This is a simple one. You just have to count the number of Fs in the given sentence.

Finished Files are the result of years of scientific study combined with the experience of years.

How many did you count?

When I got four, I have it none.
When I got two, I have it some.
When I got none, I have it all.

What is it?

Can you count the number of triangles in the picture below?

It has five wheels, though often think four, You cannot use it without that one more, You can put things in it, you can strap things on top, You can't find it in the market, but you can still go shop. What is it?

Here is a mathematical challenge that will not only engage your brain but also measure your quick-thinking abilities. If you can successfully identify the missing number in such a short span, you are demonstrating exceptional intellectual qualities.

Daniel walks into a movie theatre. While in the movie, he suddenly smiles delightfully. About a couple of minutes later, he seems shocked. He walks out of the theatre, goes to a bridge and jumps over the edge killing himself.

Why did he do it?

Note: Think Lateral