Question

Tanya drives to work every day and passes two independently operated traffic lights. The probability that both lights are red is 0.55. The probability that the first light is red is 0.69. What is the probability that the second light is red, given that the first light is red?
@mathmale

Answer 1

10 more minutes (yikess)

Answer 2

This is one of those problems for which I have to explore possibilities myself. I'd encourage you to come up with at least 2 different ways of approaching this problem and then choose one of them. Where are you now in that thought process?

Answer 3

is this conditional probability

Answer 4

At the moment I'm treating it as such. Options for the light are Red and Green/
Options for the two different lights (at 2 different intersections) are 1 and 2.

Answer 5

Can you set up a contingency table based on that?

Answer 6

uhh what would the catergories be?

Answer 7

To be frank, I'm not making very good progress on this problem.
As before, I'd say the categories are RED and GREEN for the light color; FIRST and SECOND for the stop lights in question.

Answer 8

Do you get partial credit for any work shown, even if your final answer is incorrect?
Or must you choose 1 from 4 possible answers?

Answer 9

its options

Answer 10

0.83

0.75

0.80

0.73

Answer 11

7 more mins

Answer 12

The two lights operate independently. Therefore, the prob. that both happen is P(R1)P(R2) = 0.55. If P(r1) = 0.69, what is P(r2)? Hint: divide

Answer 13

.7971?

Answer 14

This is my best, educated guess, regarding the correct way to solve this problem.
Does that match any of the choices given you?

Answer 15

Or is .7971 close to any of the choices?

Answer 16

no but if we round it to .80 then its the third option

Answer 17

Right. Go for it.

Answer 18

Thanks !!!

Answer 19

Seeing you need to go, I'm logging off myself. Hope to talk with you again really soon! Great day. Bye.