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Skyrior
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Homework Statement
I. A hundred seeds are planted in ten rows of ten seeds per row. Assuming that each seed independently germinates with probability 1/2, find the probability that the row with the maximum number of germination contains at least 8 seedlings.
II. Consider a randomly chosen n child family, where n>1. Let A be the event that the family has at most one boy, and B be the event that every child in the family is of the same sex. For what values of n are the events A and B independent?
III. A quadratic equation, [itex]ax^{2}+bx+c=0[/itex] is copied by a typist. However, the numbers standing for a, b and c are blurred and she can only see that they are integers of one digit. What is the probability that the equation she types has real roots?
IV. Two people agree to meet each other at the corner of two city streets between 1 p.m. and 2 p.m., but neither will wait for the other more than 30 minutes. If each person is equally likely to arrive at any time during the one hour period, determine the probability that they will in fact meet.
Homework Equations
binomial cumulative distribution frequency (GDC)
binomial probability distribution frequency (GDC)
Poisson probability and cumulative distribution frequency (GDC)
Independent events are such that P{A|B} = P(A) and P{B|A} = P(B)
Answer to I:
[itex] 1 - (\frac{121}{128})^{10} \approx 0.430 [/itex]
Answer to II:
[itex] n = 3 [/itex]
Answer to III:
[itex] \frac{107}{576} [/itex]
Answer to IV:
[itex] \frac{3}{4} [/itex]
The Attempt at a Solution
I:
I thought of using binomial cdf to calculate the rate for one row to have at least 8 germination, so:
One row = 1 - binomcdf(10, .5, 7)
Then we use this to calculate the rate that we have at least one row that fulfills this criteria:
All rows = 1 - binomcdf[10, (binomcdf(10, .5, 7), 0]
However, the answer doesn't seem to be this...
II:
I know why the answer is 3, but I do not know how to form an equation that can get you 3:
I tried doing this, but it does not seem to work:
Probability of [itex] A = \frac{1}{2^{n-1}} [/itex]
Probability of [itex] B = \frac{2}{n+1} [/itex]
So:
[itex] \frac{1}{2^{n-1}} = \frac{\frac{2}{n+1} \times \frac{1}{2^{n-1}}}{\frac{2}{n+1}}[/itex]
But I have no idea how to solve this equation since it cancels out itself...
III:
because [itex] b^{2} \geq 4ac[/itex]
So I have a very long list that turns out to be wrong:
For b = 1, 4ac is impossible to be 1 or lower
For b = 2, a and c must both be 1:
1/9 * 1/9 * 1/9
For b= 3:
1/9 * 3/81
etc...
IV:
Sorry, I tried to understand this question, and I used:
Dividing into 60 minutes:
1:00 p.m. = 1/60 * 1/60
1:01 p.m. = 2/60 * 2/60
etc..
1:30 p.m. = 30/60 * 30/60
1:31 p.m. = 29/60 * 29/60
etc..
I added everything up, but I did not get the answer required.
Thank you for any help :)
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