1 Answer

Richardtallent · Answer 1 · 2020-09-16T05:08:17+0000

$\frac{\textbf{1}}{\textbf{20}}$

Explanation:

Probability=
$\frac{\text{number of favourable outcomes}}{\text{total number of outcomes}}$

Probability for a randomly chosen girl to be senior=
$\frac{\text{number of senior girls}}{\text{total number of girls}}$

Probability for a randomly chosen girl to be senior=
(7)/(8+11+9+7)=(7)/(35)=(1)/(5)

Probability for a randomly chosen boy to be senior=
$\frac{\text{number of senior boys}}{\text{total number of boys}}$

Probability for a randomly chosen girl to be senior=
(9)/(10+7+10+9)=(9)/(36)=(1)/(4)

For two independent events,

Probability for both event 1 and event 2 to take place=
$\text{probability of event 1} * \text{probability of event 2}$

Since choosing boys and girls is independent,

Probability for both boy an girl chosen to be senior=
$\text{probability for boy to be senior}*\text{probability for girl to be senior}$

Probability for both boy and girl chosen to be senior=
(1)/(5) * (1)/(4) = (1)/(20)

So,required probability is
(1)/(20)

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