Help! probability 2U question (1 Viewer)

[barny268]

Hi everyone
may seem a stupid question but not sure how to do it
the probability that a connection in an alarm clock works in 0.6. a least one connection must be working for the alarm clock to work. find the minimum number of connections to ensure a 99% probability that it works.

please explain it to me. not just the answer
thanks
and good luck on monday

 

[powlmao]

Hi everyone
may seem a stupid question but not sure how to do it
the probability that a connection in an alarm clock works in 0.6. a least one connection must be working for the alarm clock to work. find the minimum number of connections to ensure a 99% probability that it works.

please explain it to me. not just the answer
thanks
and good luck on monday

I am having trouble reading the question, can you post a pic of the question?

 

[qawe]

Hi everyone
may seem a stupid question but not sure how to do it
the probability that a connection in an alarm clock works in 0.6. a least one connection must be working for the alarm clock to work. find the minimum number of connections to ensure a 99% probability that it works.

please explain it to me. not just the answer
thanks
and good luck on monday

P(at least 1 working) = 1 - P(none working) = 1 - 0.4^n
Let P = 0.99
1 - 0.4^n = 0.99
Solve for n
n = 5.03
So there needs to be at least 6 connections

 

[barny268]

ah thanks heaps makes sense

 

[BenHSC2011]

P(at least 1 working) = 1 - P(none working) = 1 - 0.4^n
Let P = 0.99
1 - 0.4^n = 0.99
Solve for n
n = 5.03
So there needs to be at least 6 connections

hey, what is the ^n for?!?! i know it means 'to the power of n...but i don't get where it comes from n stuff...

 

[michaeljennings]

hey, what is the ^n for?!?! i know it means 'to the power of n...but i don't get where it comes from n stuff...

Probability of a connection not working is 0.4, therefore for 'n' connections not to work it is (0.4)^n. And since at least one of the connections HAS to work it is it is 1 minus the possibility of none of them working therefore it is 1-(0.4)^n