A round cake can be divided into two equal parts with one straight cut, and into three equal parts with three straight cuts. What is the smallest number of cuts needed to divide it into twelve equal parts?
Editorial task: state the source’s radial-sector convention (full diameter cuts, no moving or stacking), give its construction, and explain the scope of the minimum claim.
Basil colours the letters in the slogan VIVAT KANGAROO. Different letters must have different colours, and equal letters must have the same colour. How many colours does he need?
A stout man takes 24 ducks, each weighing 2 kg, to market. He trades every two ducks for one 4-kg Muscovy duck. Then he trades each Muscovy duck for four 1-kg chickens. Next he trades every eight chickens for one 8-kg goose. Finally he trades all the geese, every two for one 16-kg piglet. How many piglets does he take home?
Luis has seven apples and two bananas. He gives Yuri two apples and receives some bananas in return. Afterwards he has equal numbers of apples and bananas. How many bananas does Yuri give him?
In the word KANGAROO, one move swaps a pair of neighbouring letters. What is the smallest number of moves needed to bring all the vowels together? The vowels are U,E,O,A,I.
Hern has 500 coins. He plans to buy five sports books and some pencils. Each book costs 80 coins and each pencil 30 coins. What is the greatest number of pencils he can buy?
The timetable below gives hours in a day (for example A 1 is 21:00 and B 3 is 09:00). Choose one cell in each column from left to right so that the selected times are in increasing order within the same day, with the A-column time earliest. Which option is correct?