If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Considering the below equation:

V + II - VI = 10
IV - X + VIII = 20
IV - VII + VI = 30

Then, I + II + III = ?

A and B have a certain number of chocolates with them. If B gives one chocolate to A, they will have an equal number of chocolates. But if A gives one chocolate to B, then A will be left with half the number of chocolates that B has.

Can you find out the number of chocolates they have right now?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

A bag contains 64 balls of eight different colours. There are eight of each colour (including red). What is the least number you would have to pick, without looking, to be sure of selecting 3 red balls?

I never stop running even when I standstill. If I am formed by joining two identical bodies together, can you guess who I am?

John killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

While preparing the table for dinner, wife came up with an idea to tease his mathematician husband. She asked her husband to pick nine toothpicks and make ten without breaking any toothpick.

The husband was also smart and did it within seconds. How ?

Which wheel of car does not rotate when you turn your car right?

I am first found in caves, now prolific online; I am a depiction, a drawing, a symbol, or sign. I will convey whichever mood you could wish; or for that matter, a fist, flask, or fish. What am I?