Question

At certain times of the year, about 70% of airline flight delays are caused by bad weather. During those times, about 50% of all flights experience bad weather, and about 25% of all flights are delayed.

Given these percentages, if the weather is good, what is the probability that your flight will be delayed?

About 15%
About 20%
About 35%
About 30%

Answer 1

hard to read and understand this, but i bet we can do it
probably easier to use numbers

Answer 2

how do you decide what numbers to use?

Answer 3

it doesn't matter
you could pick 1 and use the percents, but i find it easier to pick an nice large number like 100 flights (because finding percents of 100 is real easy) or even 1000 because sometimes you have to find percents of percents
lets use 1000

Answer 4

lets use 1000 and go slow
first it says "and about 25% of all flights are delayed."
out of 1000, how many flights are delayed, and how many are not delayed?

Answer 5

250 are delayed and 750 are not delayed

Answer 6

good

Answer 7

now what?

Answer 8

now i am thinking

Answer 9

hold on one minute sorry

Answer 10

no its fine. take your time. i appreciate your help. @satellite73

Answer 11

i got the formula, just trying to think of how to put it in to words to make it make sense

Answer 12

ok got it
you still there?

Answer 13

yeah im still here

Answer 14

ok one more minute damn

Answer 15

ok it wasn't that bad, just had to shake the cobwebs out

Answer 16

there are 1000 fights, 500 have good weather, 500 have bad
there are 750 on time and 250 delays
of the delays, 70% are from bad weather, and so 30% from good weather so 175 had bad weather and 75 had good weather

Answer 17

the probability you the flight was delayed given you had good weather is therefore
\[\frac{75}{500}=.15=15\%\]

Answer 18

Thank you! Thank you! Thank you so much! @satellite73