60http://nrich.maths.org/secondary-loweren 2012 http://nrich.maths.org/public/terms.phpThis article suggests some ways of making sense of calculations involving positive and negative numbers.http://nrich.maths.org/9958Wed, 01 Dec 1999 00:00:01 +0000http://nrich.maths.org/9954Wed, 01 Dec 1999 00:00:01 +0000Investigate different ways of making £5 at Charlie's bank.http://nrich.maths.org/9943Wed, 01 Dec 1999 00:00:01 +0000Play this game to learn about adding and subtracting positive and negative numbershttp://nrich.maths.org/9941Wed, 01 Dec 1999 00:00:01 +0000Imagine a very strange bank account where you are only allowed to do two things...http://nrich.maths.org/9923Mon, 01 Apr 2013 00:00:01 +0100I'm thinking of a rectangle with an area of 24. What could its perimeter be?http://nrich.maths.org/9691Sat, 01 Dec 2012 00:00:01 +0000Can you make sense of the three methods to work out the area of the kite in the square?http://nrich.maths.org/8301Wed, 01 Aug 2012 00:00:01 +0100Generate three random numbers to determine the side lengths of a triangle. What triangles can you draw?http://nrich.maths.org/8098Wed, 01 Aug 2012 00:00:01 +0100Six samples were taken from two distributions but they got muddled up. Can you work out which list is which?http://nrich.maths.org/7731Mon, 01 Aug 2011 00:00:01 +0100Can you decide whether these short statistical statements are always, sometimes or never true?http://nrich.maths.org/7721Mon, 01 Aug 2011 00:00:01 +0100 How can you change the area of a shape but keep its perimeter the same? How can you change the perimeter but keep the area the same? http://nrich.maths.org/7534Sun, 01 May 2011 00:00:01 +0100Have a go at creating these images based on circles. What do you notice about the areas of the different sections?http://nrich.maths.org/6468Tue, 01 Feb 2011 00:00:01 +0000This article gives a brief history of the development of Geometry.http://nrich.maths.org/6352Tue, 01 Feb 2011 00:00:01 +0000Can you work out which spinners were used to generate the frequency charts?http://nrich.maths.org/6123Mon, 01 Aug 2011 00:00:01 +0100Different combinations of the weights available allow you to make different totals. Which totals can you make?http://nrich.maths.org/5958Tue, 01 Feb 2011 00:00:01 +0000In this game the winner is the first to complete a row of three. Are some squares easier to land on than others?http://nrich.maths.org/5864Tue, 01 Feb 2011 00:00:01 +0000Can you picture how to order the cards to reproduce Charlie's card trick for yourself?http://nrich.maths.org/5775Tue, 01 Feb 2011 00:00:01 +0000Can you describe this route to infinity? Where will the arrows take you next?http://nrich.maths.org/5469Tue, 01 Feb 2011 00:00:01 +0000Draw some isosceles triangles with an area of $9$cm$^2$ and a vertex at (20,20). If all the vertices must have whole number coordinates, how many is it possible to draw?http://nrich.maths.org/2666Tue, 01 Feb 2011 00:00:01 +0000If you have only 40 metres of fencing available, what is the maximum area of land you can fence off?http://nrich.maths.org/2663Sat, 01 Dec 2012 00:00:01 +0000Charlie and Alison have been drawing patterns on coordinate grids. Can you picture where the patterns lead?http://nrich.maths.org/2292Tue, 01 Feb 2011 00:00:01 +0000How many different symmetrical shapes can you make by shading triangles or squares?http://nrich.maths.org/1868Tue, 01 Feb 2011 00:00:01 +0000How many moves does it take to swap over some red and blue frogs? Do you have a method?http://nrich.maths.org/1246Tue, 01 Feb 2011 00:00:01 +0000Liam's house has a staircase with 12 steps. He can go down the steps one at a time or two at time. In how many different ways can Liam go down the 12 steps?http://nrich.maths.org/1019Tue, 01 Feb 2011 00:00:01 +0000Charlie likes tablecloths that use as many colours as possible, but insists that his tablecloths have some symmetry. Can you work out how many colours he needs for different tablecloth designs?http://nrich.maths.org/900Wed, 01 Jun 2011 00:00:01 +0100In a three-dimensional version of noughts and crosses, how many winning lines can you make?http://nrich.maths.org/895Tue, 01 Feb 2011 00:00:01 +0000Five numbers added together in pairs produce: 0, 2, 4, 4, 6, 8, 9, 11, 13, 15 What are the five numbers?http://nrich.maths.org/481Tue, 01 Feb 2011 00:00:01 +0000