# Birthdays of grandfather and granddaughter

• frecklesan
In summary, the probability that a granddaughter will be born on the same birthdate and time as her grandfather is dependent on various factors such as the probability distribution, average life spans, and time zones. Assuming a flat probability distribution, the chances are 1 in 525,600 for the grandfather and granddaughter to have the same birthdate and time. However, this is not necessarily valid and it is important to consider the probability that they are not born in the same time period and take 1 minus that.
frecklesan
Hi to all you smart people out there: I need your help, and don't know how to solve this. If a grandfather is born on February 4, 1950 at ll:07 a.m. and his granddaughter is born on February 4, 2002 at ll:07 a.m. how do I find how the probability or stats of this happening between birthdays of grandfather and granddaughter. I really appreciate your help. Thank you very much.

do you mean the same day, hour, minute or what. the question as posed is too vague and has many possible interpretations. the simplest is, given your grandfather's DoB, then there is a chance of 1 in 365 that your granddaughter will be born on the same day in the year

It also depends on what kind of assumptions you make about average life spans, average age of parents at the time of giving birth, whether you include all time zones, and various other things.

If you have a notion of how precisely the two are aligned, and you have a probability function, then you can start using numbers.

Thanks Matt, I guess I am asking what are the chances that a grandaughter would be born on the same birthdate, and time as the grandfather? I don't know how to setup the problem. He is born 2/4 and she is born on 2/4 both at ll:07 a.m. I am not very good at math or expressing myself. Thank you.

freclesan - If you assume that the probability distribution is flat (which is not necessarily valid), then the answer is:
1/365 for the right day (since 2002 is not a leap year)
1/(365*24) for the right hour
1/(365*24*60) for the right minute
1/(365*24*60*60) for the right second
and so on.

Hi, so then if I multiply 1/(365*24*60) = 525600 (I don't think they know the seconds) then it means there is a l in 525600 of his being born on the same month, day and time (hour plus minutes) as his granddaugher, right? I really appreciate this very much. You people have made my day!

But what you have to do is work out the probability they are not born in the same time period and then take 1 minus that. It's just the old what's the probability there are two people in a class with the same birthday. For a class of 25 the probability is 50%.

Originally posted by selfAdjoint
But what you have to do is work out the probability they are not born in the same time period and then take 1 minus that. It's just the old what's the probability there are two people in a class with the same birthday. For a class of 25 the probability is 50%.

Actually, the probability for a random group of 22 people to have a pair with the same birthday is already better than 50%.

Since there are only two people in this problem - the daughter and the grandfather, it's a bit simpler.

## 1. What is the significance of celebrating the birthdays of a grandfather and granddaughter together?

Celebrating the birthdays of a grandfather and granddaughter together is a way to honor the special bond between generations and to recognize the importance of family. It is also a way to create lasting memories and strengthen familial relationships.

## 2. How do scientists study the relationship between grandparents and grandchildren?

Scientists may study the relationship between grandparents and grandchildren through various methods such as surveys, interviews, and observations. They may also analyze data from studies that have been conducted on this topic in the past.

## 3. Is there a genetic link between a grandfather and granddaughter's birthdays?

While there is no direct genetic link between a grandfather and granddaughter's birthdays, they may share certain genetic traits and predispositions due to their familial relationship. This can be further studied through genetic testing.

## 4. What impact does the relationship between a grandfather and granddaughter have on their overall well-being?

The relationship between a grandfather and granddaughter can have a positive impact on their overall well-being. Studies have shown that strong grandparent-grandchild bonds can lead to improved mental health, increased social support, and a sense of belonging.

## 5. How can families celebrate the birthdays of a grandfather and granddaughter together?

Families can celebrate the birthdays of a grandfather and granddaughter together by planning special activities or outings that both generations can enjoy. This can include a family dinner, a trip to a favorite destination, or a day spent doing activities that the grandfather and granddaughter both love.

• Set Theory, Logic, Probability, Statistics
Replies
8
Views
3K
• Precalculus Mathematics Homework Help
Replies
34
Views
2K
• Set Theory, Logic, Probability, Statistics
Replies
7
Views
2K
• Set Theory, Logic, Probability, Statistics
Replies
4
Views
2K
• Special and General Relativity
Replies
145
Views
12K
• Precalculus Mathematics Homework Help
Replies
3
Views
942
• Quantum Physics
Replies
22
Views
1K
• Set Theory, Logic, Probability, Statistics
Replies
15
Views
27K
• Set Theory, Logic, Probability, Statistics
Replies
2
Views
2K
• Set Theory, Logic, Probability, Statistics
Replies
6
Views
4K