marscole

Junior Member
10+ Year Member
May 30, 2006
347
10
Status
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
Apr 5, 2008
14
0
Status
Pre-Dental
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
Aug 15, 2008
169
0
Status
Dental Student
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 :p
 
Last edited:
OP
marscole

marscole

Junior Member
10+ Year Member
May 30, 2006
347
10
Status
yeah... thanks... i misunderstood the wordings....