Question

The probability of selecting a student who does geography is 0.2. The probability of selecting a

student who does mathematics is 0.03. Find the probability of selecting a student who does
mathematics given that he /she does geography.

Answer 1

I think you have a mistake in the way you explain there.

P(X=4) = 0.8*0.8*0.8*0.2 = 0.1024

But don't forget that there is still P(X=5), P(X=6), P(X=7), ... . It's just that our main character here (Hugo) can only buy 4, but it's still a probability that he finally get his fav player card on the tenth try right? And all of that P(X=x) , with x is a positive real number, will sum up to 1. Lets ask Sal to further explain this in another video. SO we know that :

P(X=1) + P(X=2) + P(X=3) + ... = 1

The question is P(X>=2), so you will add P(X=2) + P(X=3) + P(X=3) + ... . By using the equation of the sum of all possibilities, we can get :

P(X=1) + P(X=2) + P(X=3) + ... = 1

P(X=2) + P(X=3) + ... = 1 - P(X=1)

Explanation:

here is your answer please let me know if this is what you are looking for just say thanks