# Destroyer Q120

#### marscole

##### Junior Member
10+ Year Member
Both male and female are normal vision. Both fathers are color blind. So, what's the prob that their 1st child will be normal boy?
My answer is 50% since boy gets X (normal X or disease X) from mom and normal Y from dad. So, there must be 2 chances. X^cY or XY.

I don't understand why it comes with 25%.

Much Much Much appreciate your input!!!!

#### htkim6680

10+ Year Member
It asks that the first child will be a normal boy. You have to factor in that the probability of having a boy is 50%

#### dentrilla

10+ Year Member
Both male and female are normal vision. Both fathers are color blind. So, what's the prob that their 1st child will be normal boy?
My answer is 50% since boy gets X (normal X or disease X) from mom and normal Y from dad. So, there must be 2 chances. X^cY or XY.

I don't understand why it comes with 25%.

Much Much Much appreciate your input!!!!
you've taken the fact that hes a boy as a for sure thing. you must consider the 50% chance that the offspring could be a girl. therefore

50% boy * 50% normal = 25%

dam htkim beat me 2 it

Last edited:
OP

#### marscole

##### Junior Member
10+ Year Member
yeah... thanks... i misunderstood the wordings....