Alex, his mother, his father, and his older sister have blood type B. His younger sister and his brothers have type O. Anna, her mother, her father, and her younger brother have type A. Her sister and her older brother have type O. If Alex and Anna have three children, what is the probability at least two of them will have type O

Respuesta :

Answer:

25%

Explanation:

the probability at least two of them will have type O can be solved as follows

Let the chances be

(Chance of Alex is I^B I ) x (1-none have type O) X (Chance of Anna is I^A i)

=>>(2/3) x (1-.75 3 ) x (2/3)= 0.25

So 0.25x 100 = 25%

The blood type of the offspring is dependent on the probable blood type

their parents.

The probability that at least 2 of them will have type O is [tex]\underline{\frac{5}{144}}[/tex]

Reasons:

Alex; Both parents are [tex]I^Bi[/tex]

Anna; Both parents are [tex]I^Ai[/tex]

Alex

[tex]\left[\begin{array}{lll}&I^B&i\\I^B&I^BI^B&I^Bi\\i&I^Bi&ii\end{array}\right][/tex]

Anna

[tex]\left[\begin{array}{lll}&I^A&i\\I^A&I^AI^A&I^Ai\\i&I^Ai&ii\end{array}\right][/tex]

Probability that [tex]I^Bi[/tex] from Alex = [tex]\frac{2}{3}[/tex]

Probability that [tex]I^Ai[/tex] from Anna = [tex]\frac{2}{3}[/tex]

Probability that two have type O = [tex]\frac{2}{3}[/tex] × [tex]\frac{2}{3}[/tex] × [tex]\left(\frac{1}{4}\right)^2[/tex] = [tex]\frac{1}{36}[/tex]

Probability that three have type O =  [tex]\frac{2}{3}[/tex] × [tex]\frac{2}{3}[/tex] × [tex]\left(\frac{1}{4}\right)^3[/tex]  =  [tex]\frac{1}{144}[/tex]

Probability that at least two have type O is

[tex]P(At \ least \ 2)=\dfrac{1}{144} + \dfrac{1}{36} = \dfrac{5}{144}[/tex]

The probability that at least 2 of them will have type O is [tex]\underline{\frac{5}{144}}[/tex]

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