Edgar likes rock music and the Kangaroo contest. He replaced letters with digits in ROCK GANG and obtained 7624 3153. How is KANGAROO encrypted using the same code?
A garden is divided into identical squares. A slow snail and a fast snail start at corner S and move along its perimeter in opposite directions, at 1 m/h and 2 m/h respectively. At which marked point will they meet?
The circles are light bulbs connected as shown. Initially all are off. Touching a bulb lights it and all its neighbours. What is the least number of bulbs you must touch to light them all?
A lion is behind one of three doors. Each door bears a sentence, but only one sentence is true. Door 1: “The lion is not behind this door.” Door 2: “The lion is behind this door.” Door 3: “The sum of two and three is five.” Behind which door is the lion?
Two girls, Eva and Olga, and three boys, Adam, Isaac and Urban, play with a ball. A girl throws to the other girl or to a boy. A boy throws to another boy, but never to the boy from whom he just received it. Eva begins by throwing to Adam. Who makes the fifth throw?
Emily enters a number in each cell of the triangular table. The sum in any two cells sharing an edge must be the same. Two numbers are already entered. What is the sum of all the numbers in the table?
On Monday Alexandra shares a picture with 5 friends. For several days, everybody receiving it sends it the next day to two friends who have not seen it yet. On which day does the number of people who have seen it first exceed 100?
Four ladybugs occupy different cells of a $4\times4$ grid. One sleeps and never moves. At each whistle, the other three move to free neighbouring cells, up, down, left or right, without returning to the cell they just left. The initial position and first three results are shown. Which image might be the result after the fourth whistle?