Answer:
(b)0.56
(c)0.38
Explanation:
(a)
P(Ben Pass) =0.8
Therefore: P(Ben fails)=1-0.8 =0.2
P(Tom Pass) =0.7
Therefore: P(Tom fails)=1-0.7 =0.3
See attached for the completed tree diagram
(b)Probability that both will pass
P(both will pass)=P(Ben pass and Tom pass)
=P(Ben pass) X P(Tom pass)
=0.8 X 0.7
=0.56
(c)The probability that only one of them will pass
Since either Tom or Ben can pass, we have:
P(only one of them will pass)
=P(Ben pass and Tom fails OR Ben Fails and Tom Pass)
=P(Ben pass and Tom fails)+P(Ben Fails and Tom Pass)
=(0.8 X 0.3) + (0.2 X 0.7)
=0.24 + 0.14
=0.38