What is the largest amount of money that you can possess in change and still if someone asks you for a dollar, you won't be able to give?

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?

A man hijacks an aeroplane transporting both passengers(8 of them) and valuable cargo. After taking the cargo, the man demands nine parachutes, puts one of them on, and jumps, leaving the other eight behind. Why did he want eight?

A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

You are provided with a grid (as shown in the picture). Can you fill the squares with numbers 1-8 in a manner that none of the two consecutive numbers are placed next to each other in any direction (vertically, horizontally or diagonally?)

Jack have ten pairs of black socks, eight pairs of white socks and seven pairs of green socks. Everything is mixed in a draw. As there is no light he were not able to identify the colour of the socks. How many of the socks did he want to take to match one pair

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

In a guessing game, five friends had to guess the exact numbers of apples in a covered basket.
Friends guessed 22, 24, 29, 33, and 38, but none of the guesses was correct. The guesses were off by 1, 8, 6, 3, and 8 (in random order).

Can you determine the number of apples in a basket from this information?

Can you tell a 3D object that has just two surfaces?

Find the next number in the following series:
6, 14, 26, 98, __?