Given that a, b and c are natural numbers show that if sqrt a+sqrt
b is rational then it is a natural number. Extend this to 3
An article which gives an account of some properties of magic squares.
Pick a square within a multiplication square and add the numbers on each diagonal. What do you notice?
Janine noticed, while studying some cube numbers, that if you take
three consecutive whole numbers and multiply them together and then
add the middle number of the three, you get the middle number. . . .
When if ever do you get the right answer if you add two fractions
by adding the numerators and adding the denominators?
If for any triangle ABC tan(A - B) + tan(B - C) + tan(C - A) = 0
what can you say about the triangle?
Generalise the sum of a GP by using derivatives to make the
coefficients into powers of the natural numbers.
Can you use the diagram to prove the AM-GM inequality?
Can you work out the irrational numbers that belong in the circles to make the multiplication arithmagon correct?
What is the value of the integers a and b where sqrt(8-4sqrt3) =
sqrt a - sqrt b?
These gnomons appear to have more than a passing connection with
the Fibonacci sequence. This problem ask you to investigate some of
Fractional calculus is a generalisation of ordinary calculus where you can differentiate n times when n is not a whole number.
Generalise this inequality involving integrals.
Beautiful mathematics. Two 18 year old students gave eight
different proofs of one result then generalised it from the 3 by 1
case to the n by 1 case and proved the general result.
For which values of n is the Fibonacci number fn even? Which
Fibonnaci numbers are divisible by 3?
Can you find the values at the vertices when you know the values on the edges?
An account of some magic squares and their properties and and how to construct them for yourself.
Build gnomons that are related to the Fibonacci sequence and try to
explain why this is possible.
An article for teachers and pupils that encourages you to look at the mathematical properties of similar games.
Can you explain the surprising results Jo found when she calculated
the difference between square numbers?
A game for 2 players
Can you find the values at the vertices when you know the values on the edges of these multiplication arithmagons?
Choose four consecutive whole numbers. Multiply the first and last numbers together. Multiply the middle pair together. What do you notice?
This article for teachers describes several games, found on the
site, all of which have a related structure that can be used to
develop the skills of strategic planning.
Start with any number of counters in any number of piles. 2 players take it in turns to remove any number of counters from a single pile. The loser is the player who takes the last counter.
Triangle ABC is an equilateral triangle with three parallel lines going through the vertices. Calculate the length of the sides of the triangle if the perpendicular distances between the parallel. . . .
Start with any number of counters in any number of piles. 2 players
take it in turns to remove any number of counters from a single
pile. The winner is the player to take the last counter.
Make and prove a conjecture about the cyclic quadrilateral
inscribed in a circle of radius r that has the maximum perimeter and the maximum area.
Sets of integers like 3, 4, 5 are called Pythagorean Triples, because they could be the lengths of the sides of a right-angled triangle. Can you find any more?
What is the volume of the solid formed by rotating this right
angled triangle about the hypotenuse?
The aim of the game is to slide the green square from the top right
hand corner to the bottom left hand corner in the least number of
Jo has three numbers which she adds together in pairs. When she
does this she has three different totals: 11, 17 and 22 What are
the three numbers Jo had to start with?”
Given a set of points (x,y) with distinct x values, find a polynomial that goes through all of them, then prove some results about the existence and uniqueness of these polynomials.
Use the animation to help you work out how many lines are needed to draw mystic roses of different sizes.
Some students have been working out the number of strands needed for different sizes of cable. Can you make sense of their solutions?
A collection of games on the NIM theme
Can you see how to build a harmonic triangle? Can you work out the next two rows?
You can differentiate and integrate n times but what if n is not a whole number? This generalisation of calculus was introduced and discussed on askNRICH by some school students.
To avoid losing think of another very well known game where the
patterns of play are similar.
Equal touching circles have centres on a line. From a point of this
line on a circle, a tangent is drawn to the farthest circle. Find
the lengths of chords where the line cuts the other circles.
The incircles of 3, 4, 5 and of 5, 12, 13 right angled triangles
have radii 1 and 2 units respectively. What about triangles with an
inradius of 3, 4 or 5 or ...?
A game for 2 players with similaritlies to NIM. Place one counter on each spot on the games board. Players take it is turns to remove 1 or 2 adjacent counters. The winner picks up the last counter.
Your data is a set of positive numbers. What is the maximum value
that the standard deviation can take?
Is there a relationship between the coordinates of the endpoints of a line and the number of grid squares it crosses?
Problem solving is at the heart of the NRICH site. All the problems
give learners opportunities to learn, develop or use mathematical
concepts and skills. Read here for more information.
Can you show that you can share a square pizza equally between two
people by cutting it four times using vertical, horizontal and
diagonal cuts through any point inside the square?
Here explore some ideas of how the definitions and methods of calculus change if you integrate or differentiate n times when n is not a whole number.
ABC and DEF are equilateral triangles of side 3 and 4 respectively. Construct an equilateral triangle whose area is the sum of the area of ABC and DEF.
Show that for any triangle it is always possible to construct 3
touching circles with centres at the vertices. Is it possible to
construct touching circles centred at the vertices of any polygon?
The diagram illustrates the formula: 1 + 3 + 5 + ... + (2n - 1) = n² Use the diagram to show that any odd number is the difference of two squares.