Calculating Overall Probability?

Question

I've got what I hope is a basic probability question...in a nutshell:

Assume that an event will only occur if three conditions are met. Each condition has an individual probability of occuring...for the sake of argument, condition 1 has a 1 in 5 chance, condition 2 has a 1 in 10 chance, and condition 3 has a 1 in 20 chance.

Using the individual probabilities, how do you determine the probability of the event occuring?

Answer 1

Multiplying all 3 probabilities (supposing all 3 conditions are mutually independent).

0.2 * 0.1 * 0.05 = 0.001 = 1 ‰
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