Respuesta :
Step 1
State an expression for the probability of an event.
[tex]\text{Probability of an event occuring =}\frac{Number\text{ of required events}}{\text{Total number of events}}[/tex]Number of required events = 4
Total number of events = 7
Step 2
Find the probabilities of defective batteries with replacement and without replacement
[tex]\begin{gathered} \text{Probabilities with replacement =}\frac{4}{7} \\ \text{Probabilities without replacement =}\frac{3}{6} \end{gathered}[/tex]Step 3
Find the probabilities that both are defective.
[tex]Pr(\text{that the battery is defective) }\times\text{Pr(that the battery is defective without replacement)}[/tex][tex]\frac{4}{7}\times\frac{3}{6}=\frac{2}{7}[/tex]Hence the probability that 2 batteries selected at random without replacement are both defective is 2/7
