WILL GIVE MEDAL IF YOU TEACH ME HOW
A charity is selling raffle tickets at $10 apiece. Ten third-place winners will be drawn, each winning $20. Five second-place winners will be drawn, each winning $50. Finally, one grand prize of $200 will be awarded. If 100 tickets are sold, what is the expected value of one ticket?

- anonymous

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- schrodinger

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- misty1212

HI!!

- anonymous

Hello!

- misty1212

there is an easy way to do this, and a probability way
lets do it the easy way first

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## More answers

- anonymous

Alright. I'd also like to know how to do it the probability way. I have a whole test on these types of questions

- misty1212

ok we can do it both ways, they are actually the same, just look different

- anonymous

alright

- misty1212

first buy up all 100 tickets at $10 each
how much do you spend total?

- anonymous

$1000

- misty1212

right
and since you bought all the tickets, you win all the money
how much do you win total? (take your time on this one)

- anonymous

$650

- misty1212

looks right

- misty1212

ok so you spent $1000, got back $650 how much did you lose?

- anonymous

$350

- anonymous

(three fiddy)

- misty1212

exactly
now averaged over the (lol)

- misty1212

now averaged over the 100 tickets you bough you lost \[\frac{350}{100}=3.50\]
expected value is \(-\$3.50\)

- anonymous

ah alright. that makes a lot of sense. it just wasnt explained very well.

- anonymous

Thank you!

- misty1212

would you like to do it the probability way?

- anonymous

wait a second

- misty1212

you can see that it is the same, just looks different

- anonymous

the multiple choice answers are:
A.
–$10.00
B.
$6.50
C.
$10.00
D.
$216.67

- anonymous

i'll check my adding again

- misty1212

really??

- misty1212

no i checked it is right

- anonymous

hmmm. I'm not sure. what you said seems to make sense to me

- misty1212

i guarantee you what i said is correct

- misty1212

maybe they are not counting the amount you lose

- anonymous

thats what im thinking

- anonymous

that would be B, right?

- anonymous

if they're not counting the amount lost

- misty1212

and saying that the expected value is \(\$6.50\) which means if you spent \($10\) you lose \(\$3.50\) but that is not a true expected value

- misty1212

the expected value is the amount you win times the probability you win it, added up, but you should also include the amount you lose as a negative

- anonymous

I know. that seems weird to me

- anonymous

yours makes more sense realistically

- misty1212

because it is wrong
you would "expect" the expected value of a lottery ticket to be negative, otherwise the charity would not make any money

- anonymous

exactly

- misty1212

-3.50 to you , +3.50 per ticket to them
tell your teacher!

- anonymous

I would if i had a teacher right now. Im on the last test of my online geometry course and they didnt explain it very well at all. maybe because they have no idea what they're talking about lol

- misty1212

if this is geometry i am an old man

- anonymous

well i can hope that 6.50 is probably the right answer

- misty1212

yeah it is the only one of the bunch that makes sense, go with that one

- anonymous

I know. I was thinking the same thing

- anonymous

welcome to South Dakota state standards

- anonymous

well thanks for the help!

- anonymous

if you have the time could i get help with one more? it seems to be a little different. if not thats okay

- misty1212

sure

- anonymous

In a certain board game, a standard number cube is rolled to determine the number of spaces a player gets to move. Use the table above to determine the expected value of the number of spaces a player moves. Round the answer to the nearest tenth.

- misty1212

unless it is really geometry, because i am clueless about that

- anonymous

posting the table in just a sec

- misty1212

one "number cube" aka one die?

- anonymous

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- anonymous

yep! lol

- anonymous

this online course was so poorly designed its not even funny

- misty1212

each outcome has probability \(\frac{1}{6}\) so really all you have do to is add and divide by 6

- misty1212

\[\huge \frac{6+3+3-3-3+1}{6}\]

- misty1212

aka \[\frac{7}{6}\] and please don't tell me that is not an answer choice !!

- anonymous

I got 1.16666.... which rounds to 1.2

- anonymous

which is an answer!

- misty1212

ok i they love decimals pick that one
who writes this gibberish?

- anonymous

No clue. A lot of the time they have trouble formulating a sentence. Sometimes major grammatical errors. It's a pain in the rear

- misty1212

FLVS or some other criminal enterprise?

- anonymous

Edgenuity, aka education2020, surprisingly

- anonymous

There were so many cases where they'd say something like an angle measuring 135º or something, and then the picture of it looking like a 45º angle

- anonymous

Obviously looking acute but they swear it measures over 90º

- misty1212

imagine
remember that these questions are written mostly by middle school math teachers or (mainly) starving graduate students living on ramen noodles and beer. they are rarely checked for accuracy

- anonymous

Probably. I've had to retake tests before simply because the right answer just wasn't in the answer choices. I had to get an actual teacher from my highschool to verify that I was right and the grading system was wrong.

- misty1212

nothing like an "actual teacher" lol

- anonymous

Sorta. She prefers "Librarian"

- misty1212

you got more or is that it?

- misty1212

LOLOLOL!!!

- anonymous

well there is another but I think I got it

- misty1212

ok good luck !

- anonymous

this is getting ridiculous

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- anonymous

im just done

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