Question

Someone please help me on this type of problem, I tried multiple times but still got correct answer. :(

Answer 1

P(both girls) = 3/20

Step-by-step explanation

The probability of the event E where the teacher selects one student from each grade and both are girls is:

`P(E)=P(girl\text{ 7th)}\cdot P(girl\text{ 8th)}`

The probability of selecting a girl from 7th grade is:

`P(\text{girl 7th)}=\frac{\text{ \# of girls in 7th grade}}{\text{ \# of students in 7th grade}}=(5)/(10)=(1)/(2)`

The probability of selecting a girl from 8th grade is:

`P(\text{girl 8th)}=\frac{\text{ \# of girls in8th grade}}{\text{ \# of students in 8th grade}}=(3)/(10)`

The probability of event E is then:

`P(E)=(1)/(2)\cdot(3)/(10)=(3)/(20)`