diagonal cross multiplication method to work out mathematical calculations

this resource is a demo of how to use a mathematical short cut to work out a wide range of caluclations that can involve;
 Unit conversion e.g. m to cm, km to m, Kg to pounds and vis versa
 Scale drawing
 Currency exchange
 Similarities
 Percentages
 Ratio and proportion

it is very helpful when teaching students working at lower tier GCSE Maths and those who are not naturally fond of maths and have low confidence when tackling and solving a word problem within the context of maths or even in science contexts e.g. working numbrer of moles or masses of reactants or products.