# Thread: Vectors and simple probability

1. ## Vectors and simple probability

can anyone tell me the basics of vectors and simple probability and solve this Q for me ?

In a group of 11 boys , 7 supports United and 4 supports City .
(i) a boy is chosen at random from the group . state , as a fraction , the probability that he supports United .
(ii) on another occasion two of the eleven boys are chosen at random . calculate the probability that they both supports City , giving your answer as a fraction

2. Hello raza9990
Originally Posted by raza9990
can anyone tell me the basics of vectors and simple probability and solve this Q for me ?

In a group of 11 boys , 7 supports United and 4 supports City .
(i) a boy is chosen at random from the group . state , as a fraction , the probability that he supports United .
(ii) on another occasion two of the eleven boys are chosen at random . calculate the probability that they both supports City , giving your answer as a fraction
Here's some basic stuff on probability. And here's something about vectors.

(i) The probability is $\frac{\text{number of successful outcomes}}{\text{number of possible outcomes}}=\frac{7}{11}$

(ii) In the same way, the probability that the first one supports City is $\frac{4}{11}$. If he does, there are then 10 boys left, 3 of whom support City. So the probability that the second supports City also is $\frac{3}{10}$.

So the probability that they both support City is $\frac{4}{11}\times\frac{3}{10}= \frac{6}{55}$

(i) The probability is $\frac{\text{number of successful outcomes}}{\text{number of possible outcomes}}=\frac{7}{11}$
(ii) In the same way, the probability that the first one supports City is $\frac{4}{11}$. If he does, there are then 10 boys left, 3 of whom support City. So the probability that the second supports City also is $\frac{3}{10}$.
So the probability that they both support City is $\frac{4}{11}\times\frac{3}{10}= \frac{6}{55}$