There are **45** NRICH Mathematical resources connected to **Inequalities**, you may find related items under Algebraic expressions, equations and formulae.

Can you build a distribution with the maximum theoretical spread?

The family of graphs of x^n + y^n =1 (for even n) includes the circle. Why do the graphs look more and more square as n increases?

Find the maximum value of n to the power 1/n and prove that it is a maximum.

The symbol [ ] means 'the integer part of'. Can the numbers [2x]; 2[x]; [x + 1/2] + [x - 1/2] ever be equal? Can they ever take three different values?

Some diagrammatic 'proofs' of algebraic identities and inequalities.

By inscribing a circle in a square and then a square in a circle find an approximation to pi. By using a hexagon, can you improve on the approximation?

Take any two numbers between 0 and 1. Prove that the sum of the numbers is always less than one plus their product?

Which is the bigger, 9^10 or 10^9 ? Which is the bigger, 99^100 or 100^99 ?

Is it possible to have a tetrahedron whose six edges have lengths 10, 20, 30, 40, 50 and 60 units?

Find all positive integers a and b for which the two equations: x^2-ax+b = 0 and x^2-bx+a = 0 both have positive integer solutions.

Is the mean of the squares of two numbers greater than, or less than, the square of their means?

Can you prove our inequality holds for all values of x and y between 0 and 1?

Can you find a quadratic equation which passes close to these points?

Farey sequences are lists of fractions in ascending order of magnitude. Can you prove that in every Farey sequence there is a special relationship between Farey neighbours?

Use the diagram to investigate the classical Pythagorean means.

The challenge is to find the values of the variables if you are to solve this Sudoku.

Take a few whole numbers away from a triangle number. If you know the mean of the remaining numbers can you find the triangle number and which numbers were removed?

An inequality involving integrals of squares of functions.

Attach weights of 1, 2, 4, and 8 units to the four attachment points on the bar. Move the bar from side to side until you find a balance point. Is it possible to predict that position?

Find the maximum value of 1/p + 1/q + 1/r where this sum is less than 1 and p, q, and r are positive integers.

Sketch the graphs of y = sin x and y = tan x and some straight lines. Prove some inequalities.

Three fences of different lengths form three sides of an enclosure. What arrangement maximises the area?

Kyle and his teacher disagree about his test score - who is right?

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. . . .

Which of these continued fractions is bigger and why?

A bag contains 12 marbles. There are more red than green but green and blue together exceed the reds. The total of yellow and green marbles is more than the total of red and blue. How many of. . . .

Which rational numbers cannot be written in the form x + 1/(y + 1/z) where x, y and z are integers?

Prove that in every tetrahedron there is a vertex such that the three edges meeting there have lengths which could be the sides of a triangle.

Show that for natural numbers x and y if x/y > 1 then x/y>(x+1)/(y+1}>1. Hence prove that the product for i=1 to n of [(2i)/(2i-1)] tends to infinity as n tends to infinity.

Prove that the product of the sum of n positive numbers with the sum of their reciprocals is not less than n^2.

Show without recourse to any calculating aid that 7^{1/2} + 7^{1/3} + 7^{1/4} < 7 and 4^{1/2} + 4^{1/3} + 4^{1/4} > 4 . Sketch the graph of f(x) = x^{1/2} + x^{1/3} + x^{1/4} -x

Which is the biggest and which the smallest of $2000^{2002}, 2001^{2001} \text{and } 2002^{2000}$?

Given that u>0 and v>0 find the smallest possible value of 1/u + 1/v given that u + v = 5 by different methods.

Which is larger cos(sin x) or sin(cos x) ? Does this depend on x ?

What fractions can you find between the square roots of 65 and 67?

Find all 3 digit numbers such that by adding the first digit, the square of the second and the cube of the third you get the original number, for example 1 + 3^2 + 5^3 = 135.

Find the positive integer solutions of the equation (1+1/a)(1+1/b)(1+1/c) = 2

Two cubes, each with integral side lengths, have a combined volume equal to the total of the lengths of their edges. How big are the cubes? [If you find a result by 'trial and error' you'll need to. . . .

The familiar Pythagorean 3-4-5 triple gives one solution to (x-1)^n + x^n = (x+1)^n so what about other solutions for x an integer and n= 2, 3, 4 or 5?