# Summary

(i) Probability is a chance of an occurrence.Â(ii) If an event cannot happen, probability is zero. If an event happens then the probability is one.(iii) The probability of an event A is a number P(A) such that 0 < P(A) â‰¤ 1.

(iv) Probability is usually expressed as fraction.

(v) Probabilty of a sure event and impossible event are 0 and 1 respectively.

(vi) Probability of an event = .

(vii) The sum of all the probabilities is one.