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

A sea diver is a real show-off. He showed everyone that he can hold his breath underwater for 15 minutes.

I went to the diver and told him that I can be underwater for double the time i.e 30 minutes.
He responded that he will give me 100$ if I would be able to do it. I won 100$.

What did I do?

How many times can you subtract the number two from the number fifty?

After teaching his class all about Roman numerals (X = 10, IX=9 and so on) the teacher asked his class to draw a single continuous line and turn IX into 6. The teacher's only stipulation was that the pen could not be lifted from the paper until the line was complete.

I taste better than I can smell. Who am I?

Complete the following series. It.s very logical:

1, 4, 5, 6, 7, 9, 11, __?

If an electric train is travelling south, then which way is the smoke going?

In an interview, a boy was asked an unusual question 'How two persons sitting with a table in between them can't see each other?' He was unable to reply. Can you?

If,

A + B = C
D - C = A
E - B = C

Based on the above equations, find out the answer for:

D + F = ?

What is the four-digit number in which the first digit is one-third the second, the third is the sum of the first two, and the last is three times the second?