one probability question

[brindha_arun]

On any day in April in a certain city, the probability of rain is 50%. What is the probability of that it rains exactly 5 days during a 7 day period in April?

Originally Posted by brindha_arun

The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up heads?

[dsaqwert]

Originally Posted by brindha_arun

The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up heads?

1-(1/2)^3=7/8

[dsaqwert]

Originally Posted by brindha_arun

On any day in April in a certain city, the probability of rain is 50%. What is the probability of that it rains exactly 5 days during a 7 day period in April?

7c5/2^7

[manasi4gre]

Originally Posted by dsaqwert

On any day in April in a certain city, the probability of rain is 50%. What is the probability of that it rains exactly 5 days during a 7 day period in April? answer= 7c5/2^7

Can u give an explaination, dsaqwert?

[brindha_arun]

Hey can u explain thy strategy?

Originally Posted by dsaqwert

1-(1/2)^3=7/8

[dsaqwert]

Originally Posted by manasi4gre

Can u give an explaination, dsaqwert?

in consequtive 7 days, every day has two possibility, either it rains or not, so 7 days have 2^7 different scenarios in terms of rainy days. and in seven days there is 7c5 different ways that only 5 days is rainy
so 7c5/2^7

[dsaqwert]

Originally Posted by brindha_arun

Hey can u explain thy strategy?

at least one head in three tosses means all the probabilities - no head in three tosses

all possible outcomes has 1 probability

and no head means three tails (TTT) which has probability (1/2)^3

so 1-(1/2)^3

[manasi4gre]

Originally Posted by dsaqwert

in consequtive 7 days, every day has two possibility, either it rains or not, so 7 days have 2^7 different scenarios in terms of rainy days. and in seven days there is 7c5 different ways that only 5 days is rainy
so 7c5/2^7

It is pretty clear now.

[Dkumar]

The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up heads?
The answer is 3/8.

[Dkumar]

The probability is 1/2 that a certain coin will turn up heads on any given toss. If the coin is to be tossed three times, what is the probability that on at least one of the tosses the coin will turn up heads?
The answer is 3/8