The Math of Twins…

Guest Post from Puck:

People keep asking if we know whether we are having boys or girls.  The ultrasounds have not told us anything yet but as an engineer I feel the need to provide an answer.

After careful observation, I can state:

• There is a 75% chance that we will have a boy.
• There is a 75% chance that we will have a girl.
• There is a 50% chance we will have both a boy and a girl.

This may seem weird at first glance but bear with me as I walk through the probability math.

What we know:

Like any scary math problem we should start with the information we know:

• There are two babies in there.  (We know because we checked.)
• Each child has a 50-50 chance of being a boy or a girl.

Possible Outcomes

That gives us 4 possible outcomes each equally probable:

• 25% – Twin A is a boy, Twin B is a boy (Upper left corner)
• 25% – Twin A is a boy, Twin B is a girl (Lower left corner)
• 25% – Twin A is a girl, Twin B is a boy (Upper right corner)
• 25% – Twin A is a girl, Twin B is a girl (Lower right corner)

Three cases includes a boy and three cases include a girl.

Conclusion:

Therefore:

• In 3 out of 4 cases (75%) we have a boy.
• In 3 out of 4 cases (75%) we have a girl.

Another interesting fact:

• Half the time the Twins are the same gender.
• Half the time the Twins are of different gender.