What is next number in the pattern below:

131 517 192 123 ?

I add 5 to 9 and get 2. The answer is correct, so what am I?

There is a unique number which when multiplied by any number from 1 to 6, we will get the new number that contains the same digits only.

Can you find that number?

What is so fragile that saying its name breaks it?

What is the fastest way to double your money?

Steffi's daughter Jazelle needs to be picked up from school every day.
Steffi asks one of her colleagues to pick up Jazelle from the school. Steffi devised a password system to confirm that Jazelle goes with the correct colleague only.

The password on Monday was SJM16.
The password on Wednesday was TAW39.

What will the password be for Friday?

In two decks of cards, what is the least amount of cards you must take to be *guaranteed* at least one four-of-a-kind?

In a box, there is a jumble of 7 red balls, 6 blue balls, 5 green balls, and 4 yellow balls. What is the minimum number of balls, will you have to pick up so that you have at least 4 balls of the same colour?

What is the riddle which can be asked all day with a different correct answer each time.

A doctor and a boy were fishing. The boy was the doctor’s son, but the doctor was not the boy’s father. Who was the doctor?