'100 cars are entered for a roadworthieness test which is in two parts, mechanical and electrical. A car passes only if it passes both parts. Half the cars fail the electrical test and 62 pass the mechnical test. 15 pass the electrical but fail the mechanical test.'
What is the probabliity a car chosen at random passes overall?
I drawed a Venn Diagram attached. What I don't understand is why the intersect is calculated by 50 - 15 = 35, and why 62 is the M and E Complement region.
My intial method was to start with backwards , starting with the statement,
'15 pass the electrical but fail the mechanical test.' ---> n (E AND M') = 15
but with the statement, 62 passed mechanical and half cars fail electrical I was unsure.
I am also stuck on how it can be decuded from the quoted statement, that n ( (E AND M) = 50-15
What is the probabliity a car chosen at random passes overall?
I drawed a Venn Diagram attached. What I don't understand is why the intersect is calculated by 50 - 15 = 35, and why 62 is the M and E Complement region.
My intial method was to start with backwards , starting with the statement,
'15 pass the electrical but fail the mechanical test.' ---> n (E AND M') = 15
but with the statement, 62 passed mechanical and half cars fail electrical I was unsure.
I am also stuck on how it can be decuded from the quoted statement, that n ( (E AND M) = 50-15