How Do You figure out this MATH Problem?

Question

Okay! I was told that I'm 1/8 of Irish and 87% African -American. I gave details saying that my mom is Irish and Black and her mom is Irish and black and my mom's dad is black and my dad is black. And so therefore someone told me I'm 1/8 Irish and 87% Black. I want to know how do you figure this out? How do you work this Math problem out to know you are 1/8th of something? or 1/4th of something? or 1/3rd of something?

Answer 1

You are half your dad and half your mom.

So, if your dad is 100% black, then you're half that, which would be 50% black.

If her mom is half irish and half black, that means your mom is (1/4) irish, (1/4) black plus half of whatever her dad was.

That would make you (1/8) irish (from your maternal grandma) and (1/8) black (from your maternal grandma).

Since you're told you were 1/8 irish, that must mean your paternal grandpa (mom's dad) is 100% black.

So
From mom: (1/8) irish, (3/8) black
From dad: (1/2) black

3/8 + 1/2 = 7/8 = 87.5% black
1/8 = 12.5% irish

Answer 2

In your case, you are 1/8 Irish and (the remainder) 7/8 black. The fraction 7/8 is actually 87.5%. So saying you're 87% black (though actually it would round up to 88%) is basically the same as saying 7/8 black.

In general, to find out the ethnic percentages or fractions of somebody, you add up all the fractions of the parents, individually add together any similar ethnicities, and divide everything by 2.

For example, in my case my mother is 100% Irish and my father is half French and half Irish. So my ethnicity is:
[ (100% Irish) + (50% French + 50% Irish) ] / 2 =
[ 150% Irish + 50% French ] / 2 =
(150/2)% Irish + (50/2)% French =
75% Irish + 25% French
You can do the same with fractions and wind up with the same results (3/4 Irish, 1/4 French).

This is because you always get half of your ethnicity from your mother, and half from your father. Similarly, you could take half of their ethnicities, and THEN add up the fractions. You'll always get the same results either way, because the methods are algebraically equivalent.

Getting back to your family. If we assume the 7/8 & 1/8 is correct, and that your father is 100% black, then your mother would have to be 1/4 Irish and 3/4 black. This way you get (1/4 Irish + 3/4 black + 1/1 black) / 2 =
(1/4 Irish + 7/4 black)/2 = 1/8 Irish, 7/8 black. This would mean that her mother (your maternal grandmother) is 1/2 Irish and 1/2 black.

On a side note, there's actually no way you can be 1/3 of something. If we assume that ancestors always trace back to people of some 100% ethnicity, and a person has two and only two biological parents, then you can only work in multiples of powers of 1/2. You can't add up halves, quarters, eighths, etc. and get thirds.

EDIT: I originally wrote "African" for "black", not because I thought I had to be P.C., but because I thought geography was the defining factor here just as it is for "Irish". But then I realized that "black" can refer to ethnicities technically not from the continent and vice versa so I went with the more general term.

Answer 3

Mom's side: 1/4 Irish, 1/4 black, 1/2 black = 1/4 Irish 3/4 black
Dad's side: 100% black.
Give 50 % weight to each
50% X (1/4 Irish + 3/4 black) + 50% (black) =
1/8 Irish + 3/8 black + 1/2 black = 1/8 Irish, 7/8 black.

Answer 4

You're 100% Black, because that's a race and not a culture. You cannot know by the description you gave about how Irish you are. You need to know your grandparents on both ends of your family.


P.S. I don't get where these people are comparing Irish and Black. You can be 100% Irish AND 100% Black. Therefore, your heritage doesn't HAVE to be 1/8 and 7/8. It could just as well be 5/8 and 7/8 because we aren't talking about like things.
Region vs. Race.

Answer 5

If both of your parents are 100% Irish, you would be 100% Irish. If one was 100% Irish and the other was 100% Scottish, you would be 50% Irish and 50% Scottish. If one was 100% Irish and the other was 50% Scottish and 50% Irish, you would be 75% Irish and 25% Scottish. Basically you add up how much of each heritage your parents have and divide it by 2. So in the last example I gave, you would add up the Irish to get 150% and the Scottish is 50%, so you divide each one by 2 to get 75% and 25%.

Answer 6

You start by identifying the ethnicity of parents, grandparents, et cetera as far back as you can go. Then work toward later generations as follows: for each ancestor, his/her ethnicity is the average of the two parents. So, if your father's father's father was black, and your father's father's mother was Irish, then your father's father was 50% black and 50% Irish. You continue this process until you get to yourself. If your claim of 1/8 Irish and 7/8 black is true, then a possible source of this would be to have 7 black great-grandparents and one Irish one.

Answer 7

irish + black = 1/2
Irish/black + black = 1/2*1/2 + 1/4 irish
that + black = 1/4* 1/2 =1/8 irish = 12.5% irish
100-12.5 = 87.5% black

Answer 8

Ethnic heritage is a matter of average, with each parent contributing 50% each to the offspring.

For example, if Joe Smith’s dad is 100% black and his mom is 100% white, then both parents will contribute 50% (50% is used because there are two individuals contributing to their offspring’s racial or ethnic make-up) to Joe’s ethnicity as follows:

50% black (50% of dad’s “blackness” and 50% of
mom’s zero “blackness”)
50% white (50% of mom’s “whiteness” and 50% of
dad’s zero “whiteness”)

In your mom’s case, her ethnic/racial make-up is :

50% of her mom’s( 50% Irishness and 50%
blackness)
50% of her dad’s (100% blackness)

and therefore she is

25% Irish, 25% black from her mom
50% black from her dad

Adding the two together, your mom is

25% Irish
75% black

Now, if we combine your mom’s make-up with your dad’s, we shall get YOUR: Own Ethnic/racial make-up as follows:

50% of your mom’s (25% Irishness and 75%
blackness)
50% of your dad’s (100% blackness)

Which will make you:

12.5% Irish (or 1/8)
87.5% Black

Conclusion: Your friend (or whoever told you about your ethnicity) is correct.

For your guide to understanding the process we went through, REMEMBER THAT YOU ALWAYS GET 50% OF YOUR DAD’S ETHNICITY AND 50% OF YOUR MOM’S ETHNICITY.

Be happy and proud about your heritage!

Answer 9

Dad makes you 50% african, assuming his parents were.
Your mother is 50% african & grandmother is 50% african.
That makes your mother 75% african.
If you go back 3 generations, there were 8 people.
7 of them were black/african, I was white/Irish.