Combinatorics
the multiplication rule, arranging in order, codes, numbers whose digits meet conditions, the multiplication and addition rules together
Exercises are drawn at random from a large bank - every click gives a different set.
Solved: 0 of 10
Problem
There are 7 books, 4 notebooks and 5 pens to choose from. We choose one item from each group. In how many ways can this be done?
Problem
Four-digit numbers with all digits different are built from the digits 0, 2, 5, 6, 7, 8. How many of them are even?
Problem
How many three-digit even numbers contain exactly one digit 7 and exactly one digit 8?
Problem
How many 4-digit numbers are divisible by 5?
Problem
A coin is tossed 4 times. How many different sequences of results are there?
Problem
There are 27 runners in a race. In how many ways can the first 2 places be taken?
Problem
A queue will be formed by 8 people, Anna among them. In how many ways can they line up if Anna is to stand at the back of the queue?
Problem
How many 3-digit numbers with all digits different are divisible by 25?
Problem
How many 3-digit numbers can be built from the digits 2, 3, 4, 6, 9, if the digits must all be different?
Problem
A flag has 3 vertical stripes. Each stripe is painted in one of 8 colours, and neighbouring stripes must have different colours. The stripe next to the flagpole must be white - white is one of these colours. How many such flags are there?
This address is one particular set - everyone who opens it gets exactly the same exercises. Copy the link from the address bar and send it to the class. You can generate a new set at the top of the page.
PhiBoard is a free online whiteboard for maths
These exercises are part of it. On the board itself you can plot a function, write a formula in LaTeX, or solve a problem together with a teacher or a friend - live, in the browser. Our app is completely free.