I'm miserable at probability. Help.... :( (1 Viewer)

[Smilebuffalo]

A sample of 3 coins is taken at random from a bag containing 8 ten cent coins and 8 twenty cent coins. Find the probability that a particular ten cent coin will be chosen, if 2 ten cent and 1 twenty cent coins are chosen.

 

[Timothy.Siu]

err, 2/3?

 

[Smilebuffalo]

according to my textbook the answer is 1/10.

 

[Smilebuffalo]

bump

 

[Timothy.Siu]

A sample of 3 coins is taken at random from a bag containing 8 ten cent coins and 8 twenty cent coins. Find the probability that a particular ten cent coin will be chosen, if 2 ten cent and 1 twenty cent coins are chosen.

oh i get the question now but i still dont know how to do it. I dont really see the relevance of the 20 cent coins being taken out.
but since 2 ten cent coins are chosen, i was just thinking it should be 1/4 lol.

"i'm mixed up, somebody help me"

 

[annabackwards]

After you've chosen the specific 10 cent coin, there's 2 left to pick out the bag. The ways the 2nd 10c coint can be picked out of the rest is 7C1 and the ways the 1 twenty coin can be picked is 8C1. Total number of ways the coins can be picked is 16C3

Therefore the prob of one specific 10 coin being chosen is:
(7C1 x 8C1)/16C3
= 1/10

 

[Timothy.Siu]

After you've chosen the specific 10 cent coin, there's 2 left to pick out the bag. The ways the 2nd 10c coint can be picked out of the rest is 7C1 and the ways the 1 twenty coin can be picked is 8C1. Total number of ways the coins can be picked is 16C3

Therefore the prob of one specific 10 coin being chosen is:
(7C1 x 8C1)/16C3
= 1/10

ahhaha niceee. i'm so dumb

 

[annabackwards]

ahhaha niceee. i'm so dumb

You're not dumb, your just interpret things differently

It took me forever to understand probability lol.

I just got hammered by mxt2 probability which is such a major pain the but! 3U probability looks so easy now ><"

 

[lyounamu]

ahhaha niceee. i'm so dumb

timmy man, ur one of the best 09er mathematician along with lolokay. don't be hard on urself for gettng 1 question wrong becoz u get 1 question wrong for every 99 questions. (99% is still pretty high u know, don't be depressed)

 

[annabackwards]

timmy man, ur one of the best 09er mathematician along with lolokay. don't be hard on urself for gettng 1 question wrong becoz u get 1 question wrong for every 99 questions. (99% is still pretty high u know, don't be depressed)

Agreed

 

[Timothy.Siu]

haha thanks guys.