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Some problems in chemistry may involve units that are not in the International System of Units (SI). In such cases it may be necessary to convert from one system to another. In other cases the units being used may be within the same system but have a different prefix.

Launch Conversion of Units

A ratio is a way of comparing two or more similar quantities by writing two or more numbers separated by colons. The numbers should be whole numbers and should not include units.After reading this text you should be able to: calculate the ratio of two or more similar quantities whether or not they are expressed in the same units; divide a quantity into a number of parts in given ratios; use ratios to scale up or scale down a list of ingredients.

Launch Ratios

Ratios are an alternative way of expressing fractions. This leaflet revises ratio calculations.

Launch Ratios - Revision

There are a number of different systems of units in use. However only the modern metric system known as the International System of Units (abbreviated SI from the French Systeme International d'Unites) is widely used. This unit will outline this system.

Launch Units and Prefixes