Is this the full question?
250. 7*50=350 and the least 3-digit multiple of 10 is 100 (10*10). 350-100=250
1
P(V|A) is not 0.95. It is opposite:
P(A|V)=0.95
From the text we can also conclude, that
P(A|∼V)=0.1
P(B|V)=0.9
P(B|∼V)=0.05
P(V)=0.01
P(∼V)=0.99
What you need to calculate and compare is P(V|A) and P(V|B)
P(V∩A)=P(A)⋅P(V|A)⇒P(V|A)=P(V∩A)P(A)
P(V∩A) means, that Joe has a virus and it is detected, so
P(V∩A)=P(V)⋅P(A|V)=0.01⋅0.95=0.0095
P(A) is sum of two options: "Joe has virus and it is detected" and "Joe has no virus, but it was mistakenly detected", therefore:
P(A)=P(V)⋅P(A|V)+P(∼V)⋅P(A|∼V)=0.01⋅0.95+0.99⋅0.1=0.1085
This is really weird.
-- NONE of the situations matches the equation at the top.
-- And the equation at the top isn't even really any big deal . . .
it's <em>always</em> true, no matter what ' t ' is . If you remove all of
the parentheses and simplify it, it says that 6 = 6. Well duh !
42 = 2 * 3 * 7
So, <span>the combination for the lock is 237</span>
