## mariomintchev 3 years ago Stats Question Real estate ads suggest that 63% of homes for sale have garages, 21% have pools, and 18% have both features. What is the probability that a home for sale has: a) A pool or garage? b) Neither a pool or garage? c) A pool but no garage?

1. mariomintchev

For a I have to use the formula: P(A) + P(B) - P(A n B) =

2. Polrek

|dw:1346193475482:dw|

3. mariomintchev

Yeah, my teacher drew that out for us today. I don't really get what goes in the formula for part a though.

4. Polrek

So the entire garage circle is 63% and the entire Pool circle is 21%. But these two percentages also contain the percentage of houses which have both. So you should add together the 63% and the 21%, and subtract the 18%, which is the intersection of A and B.

5. Polrek

|dw:1346193785276:dw|

6. mariomintchev

yeah i see that now.

7. Polrek

|dw:1346193816687:dw|

8. mariomintchev

for b, do i take 37 + 79 and then subtract 82?

9. mariomintchev

or am i off?

10. Polrek

I think you should just take the complement of your answer to A.

11. Polrek

66% of houses have either a pool or a garage, so (1-0.66) = 0.44 will have none of these.

12. mariomintchev

that's not it

13. mariomintchev

i am given this formula though: P(A)=1-P(A^c)

14. Polrek

Yeah, so 1-P(A)' = P(A), and this works the other way. 1-P(A) = P(A)'

15. mariomintchev

it's 0.34. you subtracted wrong.

16. Polrek

Haha oh dear, more coffee required. Sorry. Do you get the idea though?

17. mariomintchev

yeah, i'm getting it slowly but surely. this is my first time taking stats and i just started, so i'm getting used to it.

18. Polrek

My advice is to get the hang of drawing those Venn Diagrams. They are really helpful.

19. mariomintchev

can you help me with part c too?

20. mariomintchev

hello?

21. Polrek

This area, right? |dw:1346194888234:dw|

22. mariomintchev

yeah

23. mariomintchev

is it 0.21-0.18?

24. Polrek

:)

25. mariomintchev

sweet :)