Comparison Bio Destroyer: # 81, 100, 101

[creative8401]

Hi everyone. Hope everyone's having a good day. I'm having a bit trouble in understanding the way these three problems in Biology section for DAT Destroyer are worded:

100) The question has "first child will be a normla boy" and to solve it, they compare the probability of having a son and multiplying with the probability of having the disorder.

However,

81) The question has "first daughter will be colorblind" and in this case, even thought the question has the same stem "first child/first daughter" it only compares the probability of the disease showing up, and not the probability of having the daughter, which would be 1/2

And in 101, it again looks for the probability of the disease showing up with the "couple's son".

I understand how the probabilities are found, but my question is when do you consider the probability of having a boy/girl and/or the probability of the disease showing up?

Any input would be great, and if you'd like to share a question similar in nature, it would help me understand. Thank you.

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[Mstoothlady2012]

Hi everyone. Hope everyone's having a good day. I'm having a bit trouble in understanding the way these three problems in Biology section for DAT Destroyer are worded:

100) The question has "first child will be a normla boy" and to solve it, they compare the probability of having a son and multiplying with the probability of having the disorder.

However,

81) The question has "first daughter will be colorblind" and in this case, even thought the question has the same stem "first child/first daughter" it only compares the probability of the disease showing up, and not the probability of having the daughter, which would be 1/2

And in 101, it again looks for the probability of the disease showing up with the "couple's son".

I understand how the probabilities are found, but my question is when do you consider the probability of having a boy/girl and/or the probability of the disease showing up?

Any input would be great, and if you'd like to share a question similar in nature, it would help me understand. Thank you.

81) The question says what is the probability that her first daughter will be colorblind, meaning the question is already stating that they are having a daughter so you do not need to account for the probability of having daughter. After doing the punnet square just look at daughters, you will see only 1 is colorblind out of 2. 100)

100) This question is not only asking for a normal child but also what is the probability that the normal child will be a boy. Read the sentence carefully it doesnt state in the question that they are having a boy, therefore you have to account for the probability of having a boy (1/2)

101) This question is very similar to 81. The question itself is stating that the child will be a boy all you are looking for is what are his chances of having hemophilia rather then looking for chances of the parents having a hemophillic son