Diophantine equations

There are 25 NRICH Mathematical resources connected to Diophantine equations
Lattice Points
problem

Lattice Points

Age
16 to 18
Challenge level
filled star empty star empty star
Why are there only a few lattice points on a hyperbola and infinitely many on a parabola?
Cakes and Buns
problem

Cakes and Buns

Age
11 to 14
Challenge level
filled star filled star empty star
Helen buys some cakes and some buns for her party. Can you work out how many of each she buys?
Are you kidding
problem

Are you kidding

Age
14 to 16
Challenge level
filled star filled star empty star
If the altitude of an isosceles triangle is 8 units and the perimeter of the triangle is 32 units.... What is the area of the triangle?
Letter Land
problem

Letter Land

Age
11 to 14
Challenge level
filled star empty star empty star
If: A + C = A; F x D = F; B - G = G; A + H = E; B / H = G; E - G = F and A-H represent the numbers from 0 to 7 Find the values of A, B, C, D, E, F and H.
CD Heaven
problem

CD Heaven

Age
14 to 16
Challenge level
filled star filled star empty star
All CD Heaven stores were given the same number of a popular CD to sell for £24. In their two week sale each store reduces the price of the CD by 25% ... How many CDs did the store sell at each price?
Deep Roots
problem

Deep Roots

Age
14 to 16
Challenge level
filled star filled star filled star
Find integer solutions to: $\sqrt{a+b\sqrt{x}} + \sqrt{c+d.\sqrt{x}}=1$
Plutarch's Boxes
problem

Plutarch's Boxes

Age
11 to 14
Challenge level
filled star filled star empty star
According to Plutarch, the Greeks found all the rectangles with integer sides, whose areas are equal to their perimeters. Can you find them? What rectangular boxes, with integer sides, have their surface areas equal to their volumes?
In particular
problem

In particular

Age
14 to 16
Challenge level
filled star filled star empty star
Can you find formulas giving all the solutions to 7x + 11y = 100 where x and y are integers?
Whole Numbers Only
problem

Whole Numbers Only

Age
11 to 14
Challenge level
filled star filled star empty star
Can you work out how many of each kind of pencil this student bought?
Not a Polite Question
problem

Not a Polite Question

Age
11 to 14
Challenge level
filled star filled star empty star
When asked how old she was, the teacher replied: My age in years is not prime but odd and when reversed and added to my age you have a perfect square...