SOLUTION: I dont know where to begin with this, please help me! After you complete this exam, you and two friends decide to go to McDonald�s to celebrate. Last month McDonald�s filled 9

Question 21656: I dont know where to begin with this, please help me!
After you complete this exam, you and two friends decide to go to McDonald�s to celebrate. Last month McDonald�s filled 90% of the orders accurately. What is the probability that:
a) All three orders will be filled accurately?
b) None of the three orders will be filled accurately?
c) At least 2 of the 3 orders will be filled accurately?

Answer by longjonsilver(2297) (Show Source): You can put this solution on YOUR website!
P(fulfilling an order successfully) = 0.90 and
P(not...) = 0.10

So,
a) P(all 3 successful) = P(first OK) and P(second OK) and P(third OK)
--> 0.90 * 0.90 * 0.90
--> 0.729

b) P(none successful) = P(first not) and P(second not) and P(third not)
--> 0.10 * 0.10 * 0.10
--> 0.001

c) P(at least 2 of the 3) means a few things: It means...
1. P(first OK) and P(second OK) and P(third OK)
OR
2. P(first OK) and P(second OK) and P(third not)
OR
3. P(first OK) and P(second not) and P(third OK)
OR
4. P(first not) and P(second OK) and P(third OK)

1. is answer to a).
Next three versions (2, 3, 4) are each 0.90*0.90*0.10 --> 0.081.

As there are 3 different routes to get to it... 2, 3 or 4, so the probability is 3*0.081 --> 0.243.

So total probability of getting 2 or more orders correct is 0.729 + 0.243
--> 0.972

jon.
RELATED QUESTIONS
Please, please help! After you complete this exam, you and two friends decide to go to (answered by stanbon)

3X to the fourth power =300. PLease help me figure this problem.. Thank you... (answered by drk)

Hi, I'm stuck on this problem and dont know where to begin. Can any tutor help me... (answered by ewatrrr)

can u please help i have went blank and dont even know where to begin with this problem... (answered by rfer)

Can you please help me with this I don't even know where to begin Solve the following... (answered by Becky0427)

Please solve algebraically: {{{x^2 +7x - y = 12 - y^2}}} {{{x^2 + y^2 + 6x + 3y =... (answered by Sphynx pinastri)

{{{16x^4yxy^3x^9x}}} I just dont know where to even start with this problem. Please... (answered by Alan3354)

please help me solve this.. i don't even know where to begin. :( {{{ 14 - d = (-7) +... (answered by Earlsdon,MrTillman)

please help me on this question. I was able to get all the others, i just don't know... (answered by Fombitz)