Question

Tasha is in the Sun Club. there are 21 student in the Club. two of them would be picked at random to attend and award banquet. what is the probability that Tasah will not be randomly chose to attend the banquet ?

Answer 1

First, notice that the probability that Tasha is picked first to attend the banquet is:

$P(1st)=\frac{1}{21}$

then, the probability to be picked second is:

$P(2nd)=\frac{1}{20}$

then, the probability to get picked to attend the banquet is:

$P(1st\cup2nd)=\frac{1}{21}+\frac{1}{20}=\frac{41}{420}$

then, the probability that Tasah will not be randomly chosen is:

$P(\text{not chosen)=}1-P(1st\cup2nd)=1-\frac{41}{420}=0.90$

therefore, the probability to not be chosen is 0.90 = 90 %