Destroyer Problem

[Awuah29]

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Hi guys,
this problem is from destroyer, and I always get it wrong. The answer is 25% , but I always get 50% .
Bill and Ann have normal vision, but their fathers are both colorblind . What is the probability that their first child will be a normal boy?

If you cross

X Y
Xc XcX XcY
X XX XY

Lookin at the boys, I m looking at 50% to 50%. Am I missing something?

 

[yakuza]

Hi guys,
this problem is from destroyer, and I always get it wrong. The answer is 25% , but I always get 50% .
Bill and Ann have normal vision, but their fathers are both colorblind . What is the probability that their first child will be a normal boy?

If you cross

X Y
Xc XcX XcY
X XX XY

Lookin at the boys, I m looking at 50% to 50%. Am I missing something?

They have a 50% chance of getting a boy, and 50% of boys are infected

 

[Awuah29]

Hi guys,
this problem is from destroyer, and I always get it wrong. The answer is 25% , but I always get 50% .
Bill and Ann have normal vision, but their fathers are both colorblind . What is the probability that their first child will be a normal boy?

If you cross

X Y
Xc XcX XcY
X XX XY

Lookin at the boys, I m looking at 50% to 50%. Am I missing something?

The answer in 25% according to destroyer. Can anyone explain?

 

[yakuza]

The answer in 25% according to destroyer. Can anyone explain?

Cmon man. Read the question more carefully. What are the chances of them having a boy? 50%

Out of 50%, what are the chances of the boys being infected? 50%

so .50 x .50 = .25

 

[Awuah29]

Cmon man. Read the question more carefully. What are the chances of them having a boy? 50%

Out of 50%, what are the chances of the boys being infected? 50%

so .50 x .50 = .25

Thanks dude,
just misread the problem