Place all the sixteen pieces shown in the illustration on a 4x4 board so
that none of horizontal and vertical rows, and none of two main diagonals
contains two pieces of the same shape or of the same color.

Suppose a snail is climbing up a slippery 30 cm wall. Each minute it
climbs 5 cm, but slides back 4 cm. How many minutes will it take the snail
to reach the top of the wall?

There is a set of nine identical weights and simple scales (without any
measures) - just as shown in the illustration. It is known that one weight
is a little bit heavier than the eight others. Using only the scales can
you identify the heavier weight in two weighings only?

There are 3 cups and 3 objects - a coin, a bean and a shell.
1) To the left of the red cup is the green cup.
2) To the left of the bean is the coin.
3) To the right of the shell is the blue cup.
4) To the right of the blue cup is the bean.
In which cup is the coin?

Suppose there is a bag of 3 checkered, 3 tweed and 2 white socks. Suppose
you reach in without looking and pull out a sock. How many times must you
reach into the bag and pull out a sock to be certain to get two socks the same
color?

Suppose seven dice are stacked as shown, and you can see all the exposed
faces, including the Back view shown in the upper right corner. Find the
sum of the pipe on the hidden faces of the dice.

This puzzle was described by Edouard Lucas at the end of the 19th century.
Place three quarters and three pennies in a line of seven cells as shown
in the Start Position above - quarters on the left, and pennies on the
right. The middle cell is empty. Now interchange two groups of coins
moving quarters to the right and pennies to the left (Finish Position).
The middle cell has to be empty when you finish. Coins are moved just in a
forward direction. This means you have to move quarters to the right and
pennies to the left only. A move consists of moving a coin on the adjacent
vacant cell, or jumping over an adjacent coin on the vacant cell
immediately behind it.

Write the numbers 1 through 8 in the circles of the grid shown in the
illustration so that no two numbers inside circles joined by a line differ
by 1. For example, if you put a 4 in the top circle, you cannot put a 3 or
a 5 in any of the circles in the row directly below it because each of
those three circles is joined to the top one by a line.

Write four 1’s and three 2’s in the empty circles so that no three numbers
that are beside each other on the big circle, have a sum that is divisible
by three.

Six pennies are placed on the table to form the triangle shown in the
Start Position. By sliding one penny at a time move them to form the shape
shown in the Final Position. You can only move one penny at a time,
without disturbing any other penny. When you move a penny, it has to be
moved to a position where it touches two other. The pennies have to stay
flat on the table at all times.

This game is the same as ordinary tic-tac-toe, except that at each turn
the player can choose to play an X or an O. You win if you get three X’s
in a row, or three O’s in a row with your turn. If the first player
doesn’t make any mistakes, he or she can always win.

There are four small equilateral triangles in the shape shown in the
illustration. Puzzle 1. Move four matchsticks and make three
non-overlapping parallelograms that are exactly the same. Puzzle 2. Move
three matchsticks and make two non-overlapping quadrilaterals that are
exactly the same.

A chessboard can be fully covered with 32 dominoes in size of two adjacent
squares on the board. Suppose we cut off two corner squares of the
chessboard as shown in the illustration. Now the question is if it's
possible to cover entirely this new board (now consisting of just 62
squares) with the 31 dominoes?

Take sixteen matchsticks and arrange them into five squares as shown in
the illustration. The object is to move two matchsticks to new positions
to get exactly four identical squares instead of five.

Exchange the black knights with the white knights as shown in Figure 1 in
the minimum possible number of moves. One move is a normal knight's move
on any vacant cell of the board.

Arrange nine identical coins into the right
triangle shown in the illustration. Change the triangle into a square by
moving the minimum of the coins. How many coins will you need to move to
do this?

Place all the numbers from 1 to 6 in the circles along the sides of the
triangle (one number per circle), so that three numbers on each side add
up to the same total - a magic sum. There are four different magic sums
that could be reached for this puzzle. All these sums are from 9-12 number
range. Can you find all of them?