the probabilities of a boy passing English and Mathematics tests are x and y. What is the probability of failing both tests(a)1-(x-y)+xy(b)1-(x+y)-xy(c)1-(x+y)+xy(d)1-(x-y)-xy
2 answers
1-(x+y)+xy
Solution.
P(pass English)= a
P(pass Maths)=b
P(Both pass)= (1+a)(1+b)
P(Both fail)=(1-a)(1-b)
=1 -b-a+ ab
=1-(b+a)+ab
P(pass English)= a
P(pass Maths)=b
P(Both pass)= (1+a)(1+b)
P(Both fail)=(1-a)(1-b)
=1 -b-a+ ab
=1-(b+a)+ab