Basil wants to paint the slogan VIVAT KANGAROO on a wall. He wants different letters to be coloured differently, and the same letters to be coloured identically. How many colours will he need?
Sally can put 4 coins in a square built with 4 matches (see picture). At least how many matches will she need in order to build a square containing 16 coins that do not overlap?
In a plane, the rows are numbered from 1 to 25, but there is no row number 13. Row number 15 has only 4 passenger seats, all the rest have 6 passenger seats. How many seats for passengers are there in the plane?
When it is 4 o’clock in the afternoon in London, it is 5 o’clock in the afternoon in Madrid and it is 8 o’clock in the morning on the same day in San Francisco. Ann went to bed in San Francisco at 9 o’clock yesterday evening. What was the time in Madrid at that moment?
The upper coin is rotated without slipping around the fixed lower coin to a position shown on the picture. Which is the resulting relative position of kangaroos?
One balloon can lift a basket containing items weighing at most 80 kg. Two such balloons can lift the same basket containing items weighing at most 180 kg. What is the weight of the basket?
Vivien and Mike were given some apples and pears by their grandmother. They had 25 pieces of fruit in their basket altogether. On the way home Vivien ate 1 apple and 3 pears, and Mike ate 3 apples and 2 pears. At home they found out that they brought home the same number of pears as apples. How many pears were they given by their grandmother?
Lisa has 8 dice with the letters A, B, C and D, the same letter on all sides of each die. She builds a block with them. Two adjacent dice always have different letters. What letter is on the die that cannot be seen on the picture?
There are five cities in Wonderland. Each pair of cities is connected by one road, either visible or invisible. On the map of Wonderland, there are only seven visible roads, as shown. Alice has magical glasses: when she looks at the map through these glasses she only sees the roads that are otherwise invisible. How many invisible roads can she see?
The positive integers have been coloured red, blue or green: 1 is red, 2 is blue, 3 is green, 4 is red, 5 is blue, 6 is green, and so on. Renate calculates the sum of a red number and a blue number. What colour can the resulting number be?
Look at the pictures. Both shapes are formed from the same five pieces. The rectangle measures 5 cm × 10 cm, and the other parts are quarters of two different circles. The difference between the perimeter lengths of the two shapes is
Place the numbers from 1 to 7 in the circles, so that the sum of the numbers on each of the indicated lines of three circles is the same. What is the number at the top of the triangle?
A rubber ball falls vertically through a height of 10 m from the roof of a house. After each impact on the ground it bounces back up to 4/5 of the previous height. How many times will the ball appear in front of a rectangular window whose bottom edge has a height of 5 m and whose top edge has a height of 6 m?
There are 4 gearwheels on fixed axles next to each other, as shown. The first one has 30 gears, the second one 15, the third one 60 and the last one 10. How many revolutions does the last gearwheel make, when the first one turns through one revolution?
A regular octagon is folded in half exactly three times until a triangle is obtained, as shown. Then the apex is cut off at right angles, as shown in the picture. If the paper is unfolded what will it look like?