Sam painted the 9 squares with the colours black, white and grey as shown. At least how many squares does he need to repaint so that no two squares with a common side have the same colour?
There are 10 ducks. 5 of these ducks lay an egg every day. The other 5 lay an egg every second day. How many eggs do the 10 ducks lay in a period of 10 days?
Each plant in John's garden has either 5 leaves, or 2 leaves and 1 flower. In total, the plants have 6 flowers and 32 leaves. How many plants are there?
Alva has 4 paper strips of the same length. She glues 2 of them together with a 10 cm overlap, and gets a strip 50 cm long. With the other two paper strips, she wants to make a strip 56 cm long. How long should the overlap be?
Every day Mary writes down the date and calculates the sum of the digits written. For example, on March 19 she writes 19.03 and calculates 1 + 9 + 0 + 3 = 13. What is the largest sum that she calculates during a year?
On Jump Street, there are 9 houses in a row. At least one person lives in each house. Any two neighbouring houses together are inhabited by at most six people. What is the largest number of people that could be living on Jump Street?
Lucy and her mother were both born in January. Today, March 19 2015, Lucy adds the year of her birth, the year of her mother's birth, her age, and her mother's age. What result does she get?
Each of the 9 segments in the figure is to be coloured either blue, green or red. The sides of every triangle are to have different colours. Three of the segments have already been coloured, as shown. What colour can the segment marked with x have?
In a bag there are 3 green apples, 5 yellow apples, 7 green pears and 2 yellow pears. Simon randomly takes fruits out of the bag one by one. How many fruits must he take out in order to be sure that he has at least one apple and one pear of the same colour?
A new chess piece “kangaroo” has been introduced. In each move, it jumps either 3 squares vertically and 1 horizontally, or 3 squares horizontally and 1 vertically, as shown in the picture. What is the minimum number of moves the kangaroo needs in order to go from its current position to the square marked with A?