## anonymous one year ago 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?

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1. misty1212

HI!!

2. anonymous

Hello!

3. misty1212

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

4. 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

5. misty1212

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

6. anonymous

alright

7. misty1212

first buy up all 100 tickets at $10 each how much do you spend total? 8. anonymous$1000

9. 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)

10. anonymous

$650 11. misty1212 looks right 12. misty1212 ok so you spent$1000, got back $650 how much did you lose? 13. anonymous$350

14. anonymous

(three fiddy)

15. misty1212

exactly now averaged over the (lol)

16. misty1212

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

17. anonymous

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

18. anonymous

Thank you!

19. misty1212

would you like to do it the probability way?

20. anonymous

wait a second

21. misty1212

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

22. anonymous

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

23. anonymous

24. misty1212

really??

25. misty1212

no i checked it is right

26. anonymous

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

27. misty1212

i guarantee you what i said is correct

28. misty1212

maybe they are not counting the amount you lose

29. anonymous

thats what im thinking

30. anonymous

that would be B, right?

31. anonymous

if they're not counting the amount lost

32. 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

33. 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

34. anonymous

I know. that seems weird to me

35. anonymous

yours makes more sense realistically

36. 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

37. anonymous

exactly

38. misty1212

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

39. 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

40. misty1212

if this is geometry i am an old man

41. anonymous

well i can hope that 6.50 is probably the right answer

42. misty1212

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

43. anonymous

I know. I was thinking the same thing

44. anonymous

welcome to South Dakota state standards

45. anonymous

well thanks for the help!

46. anonymous

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

47. misty1212

sure

48. 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.

49. misty1212

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

50. anonymous

posting the table in just a sec

51. misty1212

one "number cube" aka one die?

52. anonymous

53. anonymous

yep! lol

54. anonymous

this online course was so poorly designed its not even funny

55. misty1212

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

56. misty1212

$\huge \frac{6+3+3-3-3+1}{6}$

57. misty1212

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

58. anonymous

I got 1.16666.... which rounds to 1.2

59. anonymous

60. misty1212

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

61. 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

62. misty1212

FLVS or some other criminal enterprise?

63. anonymous

Edgenuity, aka education2020, surprisingly

64. 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

65. anonymous

Obviously looking acute but they swear it measures over 90º

66. 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

67. 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.

68. misty1212

nothing like an "actual teacher" lol

69. anonymous

Sorta. She prefers "Librarian"

70. misty1212

you got more or is that it?

71. misty1212

LOLOLOL!!!

72. anonymous

well there is another but I think I got it

73. misty1212

ok good luck !

74. anonymous

this is getting ridiculous

75. anonymous

im just done