the events a and b are independent , the probability that event a occurs is greater than 0 , and the probability that event a occurs is twice the probability that event b occurs . the probability that at least one of events a and b occurs is 5 times the probability that both events a and b occur . what is the probability that event a occurs ?
let us say probability of a occuring is a . let us say probability of b occuring is b . a = 2 b probability ( either a or b or both ) = 5 times probability ( a and b ) a * ( 1 - b ) + b * ( 1 - a ) + ab = 5 * ab substituting a = 2 b in the second equation : 2 b * ( 1 - b ) + b * ( 1 - 2 b ) + 2 b * b = 5 * 2 b * b 3 b - 2 b ^ 2 = 110 b ^ 2 3 b = 12 b ^ 2 b = 3 / 12 = 1 / 4 so , a = 2 b = 1 / 2
multiply(divide(add(const_2, const_1), add(multiply(5, const_2), const_2)), const_2)