Check out the midterm my students are taking tomorrow...

[gray_ghost]

1. Suppose a couple has two children. Find the probability that both children are boys if it is known that:
(a) At least one of the children is a boy
(b) The older child is a boy

Hint: The space of all possible outcomes is S = { bb,bg,gb,gg }

2. Suppose a student dormitory consists of:
60% first-year students (10% of whom own a car)
40% second-year students (20% of whom own a car)
Find the probability that a randomly selected student in the dormitory owns a car.

3. The Pentagon computer which you hacked into in the last homework assignment has become self-aware, and has come to the conclusion that human beings are a lower form of life which must be eradicated. To this end, it is attempting to guess the nuclear launch codes for all the nuclear missiles in the US nuclear arsenal (over which it has omniscient control).

The launch codes are of the form: XXX-XXX-XXX
The first block can be any combination of letters or digits.
The last two blocks must be numbers.

If the computer can try 2,000,000 codes a minute, how many minutes will it take before all possible codes have been tried?

4. If one card is drawn from a deck of 52 playing cards, what is the probability that you do NOT draw a face card or a heart?

5. In South Dakota Hot Lotto, 5 balls are drawn from one drum (the balls are 1-39), and a Hot Ball is chosen from a second orange drum (Hot Balls are numbered 1-19). What is the probability of picking all 5 numbers + Hotball?

6. Write down your first name. How many different permutations in the letters of your name are there?

7. If a coin is flipped 12 times, what is the probability that you get exactly 4 heads?

8. What is the probability that the sum of two rolled six-sided dice (numbered 1-6) is 10 or greater given that at least one of the rolled dice is a 5?




I just realized something. I am totally going to have to flock my journal in the future if I continue to teach. It is way too dangerous to have an open blog out there with a bunch of students who are probably online all the time, googling for their professor because they are bored and curious. *sigh*

Well for now - just this entry.

Comments

[phendog.livejournal.com]

1) bb, bg = .5
2)=0.4*(0.2)+0.6*(0.1)= .14
3) =(36*36*36*10^6)/2000000=23328 minutes (assuming the computer doesn't find the answer before that and quit looking!)
4) 30/52 or 0.5769
5) =1/39*1/38*1/37*1/36*1/35*1/19 = 7.6^-10
6) *is embarrassed to admit that I don't really understand this question, but I'll try* AMBER = 5!, = 120 combinations of letters?
7) Ugh. I don't remember the formula for this, and I'm WAY too lazy to figure it out longhand. So I'm going to take the loser way out and say 4/12 = 0.33 for partial credit?
8) 2/6 = .33


So...how did I do? Honestly, I hated that class...hence why I can't remember most of the more advanced formulas.

[glimmergirl.livejournal.com]

*skips the mathy bit because it's been WAY too long since I understand even parts of stuff like that*

:)

I try to keep the public parts of my journal as non-identifiable as possible, and right now pretty much only my writing, graphics and a meme every now and then is in a non-locked post. While I don't think any of my past or future students would be able to find me, you never know. It's just easier to not have to worry about losing your privacy.

[katekat]

y'know, I didn't even think about that - I guess I'm used to the idea that you actually can't find people you're looking for in cyberspace, unless you know where to look...

Do you have any personal identifiers in your User Info? Especially stuff that students might know? I thought you only used/mentioned your university contact info to them. It's not like your handle's "This is the LJ of Tyler Wilson" or anything....