A bookshelf has 17 books on top, 15 in the middle and 7 on the bottom. Monika wants equal numbers on the three shelves while moving as few books as possible. How many books must she move from the middle to the bottom?
Six children race. Ariadne finishes third. Bill finishes sixth, just behind Ernest. Fatima finishes between Ariadne and Ernest. Diana overtakes Charles just before the finish. Who wins?
A three-part unfolded card has numbers in the centre and holes in the left and right panels. Mike folds the right panel onto the centre and sees 2,3,5,6 through its holes. He then folds the left panel over both. What is the sum of the numbers still visible?
Three turtles race 10 km, each at constant speed. When the first finishes, the second has travelled one quarter of the distance and the third one fifth. How far is the third from the finish when the second finishes?
Vera replaces the two question-mark cubes by numbered cubes. Each number must be at least 2 greater than the number immediately below it. How many ways are possible?
Each of the five spinners is divided into equal-sized sectors, with different numbers of sectors. Anna wins when the pointer stops on a dark sector. Which spinner gives the best chance?
Five swimmers swim the same distance in a relay, one after another without stopping. The stopwatch shows the cumulative time after each swimmer, beginning with 2 minutes 8 seconds for the first. Which swimmer is fastest?
Jana cuts four equal small squares from the corners of a square sheet. The removed area totals 16 cm² and the remaining cross has area 9 cm². What is the perimeter of the cross?
The figure consists of equal squares. B is midway between A and C; D is midway between C and E. Maria draws a straight line from S to one of A–E to divide the figure into equal areas. Which point must she choose?
Hassan fills each cell with 0 or 1. Every row, column and the two main diagonals must sum to exactly 3. A zero is already entered. What is the sum in the question-mark cells?
A witch has 10 apples,9 bananas and 6 pears. She transforms every fruit into a different type; an apple becomes a banana or pear. Afterwards she has 15 apples,7 bananas and 3 pears. How many apples became bananas?