One sixth is about 17 per cent, so if you tossed a dice 100 times, you would expect to roll a five about 17 times. Weighing up pluses and minuses One of the simplest ways to weigh up risks and benefits is to add up the consequences multiplied by the probability that they will happen. This gives you an overall expected outcome, as shown in the following example. There is a 1 in 100 chance of choosing a particular ticket. The probability of more than one event happening You can calculate the chances of more than one independent event happening by multiplying together the chances of each one happening.
Many factors influence how people perceive risks and make decisions.
More people worry about travelling by plane than by car, even though statistics show that they are 10 times more likely to be killed in a car travelling between two cities than in a commercial airline flying the same journey. Our perception of risk is often based on how dreadful we think a risk is and how well we understand the risk, rather than on probabilities. Using mathematics to analyse risks and benefits and to analyse the probability of an event occurring can help us make decisions. But we still have to decide how to measure the benefits and risks, and how best to weigh up the options. The Australian Foundation for Science and the Science and Technology Awareness Program of the Commonwealth Department of Industry, Science and Resources are also supporters of Nova .