Currently viewing the tag: "Permutations and combinations"
A container holds 4 yellow balls, 2 blue balls and a red ball. The balls are identical in all ways except colour. When you shake the container the balls settle into a hexagonal pattern as shown in the diagram.
You win if two blue balls touch.
How many different ways can […]
(a) You must mark four red squares and five blue squares in a 3 by 3 grid .
How many ways can you do this so that all the rows columns and diagonals have an even number of red squares?
Two solutions are considered the same if one can be transformed to […]
If you change the order of these digits you can get 24 different numbers, for example 2547, 2574, 2745, … Can you find all 24 different numbers made by using each of the digits 2, 4, 5, 7 just once?
How many of these numbers have 2 in the thousands place? How many have 2 […]
A photographer is taking photographs.
She has to arrange the people in two rows one behind the other in order of height.
Each person at the back must be taller than the person directly in front of them.
Along the rows the heights must increase from left to right.
How many different arrangements are there […]
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