i am noob at probability! XD

• davidche

  23 Oct 08, 20:35

  In a game, 2 dices are thrown together. Die A has 2 red faces and 4 blue. Die B has 4 red and 2 white faces. Find the probability that there is at least one red face on top.

  Could you guys do the working out? btw i wasnt tot the textbook way. XD

• deteq

  23 Oct 08, 20:42

  P(at least one red face)= (2/6 * 4/6) + (2/6 * 2/6) + (4/6 * 4/6)

  = 7/9

  correct or not ah.

• kenn3th

  23 Oct 08, 20:52

  correct.

  alternatively you can find the other one without any red.

  so it's 4/6 x2/6 = 2/9

  1 -2/9

• Ferrari_RoXz

  23 Oct 08, 20:54

  Originally posted by deteq:

  P(at least one red face)= (2/6 * 4/6) + (2/6 * 2/6) + (4/6 * 4/6)

  = 7/9

  correct or not ah.

  
  Ya, shld be correct. I got the same answer as you.

• deteq

  23 Oct 08, 20:55

  yay! tomorrow no fear

• davidche

  23 Oct 08, 21:03

  hehe correct. same as ans key

• iamapebble

  23 Oct 08, 21:20

  I got question I got question!
  
  If they ask such questions like at least one red or something even though you have like R,B, you also have to include B,R. Is there any case where you won't have to? Is it when you replace the thing uh? Scared tomorrow suddenly cannot do. ^^"

• Garrick_3658

  23 Oct 08, 21:31

  Draw tree diagram bah.

• charlize

  23 Oct 08, 21:37

  All you need is to pick up gambling and your probability skills will improve.

   

  Try Blackjack, Big-small, Roulette, Caribbean Stud Poker, Craps etc

• eagle

  23 Oct 08, 21:46

  More probability questions here... although still not a lot yet :(

  http://examworld.blogspot.com/search/label/O%20lvl%20EM%3A%20Probability

• davidche

  23 Oct 08, 22:24

  Originally posted by iamapebble:

  I got question I got question!
  
  If they ask such questions like at least one red or something even though you have like R,B, you also have to include B,R. Is there any case where you won't have to? Is it when you replace the thing uh? Scared tomorrow suddenly cannot do. ^^"

  denominater minus one right>?

  I know i suck in probability but even when u times 2 to P when you are looking for Either One, it is essentially P+ P

  So when there is no replacement, you just -1 from the denominater and do the same P + P(denom - 1) lo.

• davidche

  23 Oct 08, 22:32

  gosh i am still havin problems with probability. I will not go to sleep unless i have this cleared in my mind.

• davidche

  23 Oct 08, 22:42

  P(at least one red face)= (2/6 * 4/6) + (2/6 * 2/6) + (4/6 * 4/6)

  = 7/9

  why is it (4/6 * 4/6)

   shldnt it be 4/6 *1  +  2/6 *1?

• Creeed

  23 Oct 08, 23:05

  4/6 * 4/6 is when die A shows a blue face and when die B shows a red face. think of all the possibilities where you have at least 1 red.

   

  Both red. die A red only or die B red only.