probability 2?
. If three persons are randomly selected , whats the probability that two were born on Monday and the other on Tuesday?
2. If Jack studies for tmr's test the prob. of getting a pass is 4/5 , if he doesnt study for it , the prob of getting a pass is 1/10. Given the prob. for Jack to study the test is 7/8 , find the prob. that he will fail the test .
3. Bag A contains black and white chess pieces.If one chess piece is drawn at random from the bag,the prob.of drawinga white chess piece and a black one are p and q respectively. (THE ANSWERS FOR P AND Q ARE 2/3 AND 1/3 RESPECTIVELY.)
(a)Bag B contains 6 white chess pieces and 8 black chess pieces.One chess piece is drawn at random from bag A and is put to Bag B,the one chess piece is drawn at random from Bag B.Find the prob.that the chess piece drawn from bag B is white. (THIS IS CHALLENGING!)
FOR NO.1,ANS=3/343
FOR NO.2,ANS=23/80
FOR NO.3,ANS=4/9
CHECK THE ANSWERS FIRST!AND EXPLAIN;)
SO MANY THANKS:D
1 個解答
- YA HOO!知識+管理員Lv 65 年前最愛解答
1.
First, select 2 persons which were born on Monday [ C(3,2) (1/7)² ]
Second, select 1 person which was born on Tuseday [ C(1,1) (1/7) ]
The probability
= C(3,2) (1/7)² C(1,1) (1/7)
= 3/343
2.
Condition 1:Jack studies for tmr's test and fail the test
The probability = (7/8)(1 - 4/5)
Condition 2:Jack doesn't studies for tmr's test and fail the test
The probability = (1 - 7/8)(1 - 1/10)
∴ The probability
= (7/8)(1 - 4/5) + (1 - 7/8)(1 - 1/10)
= 23/80
3.
Bag A contains black and white chess pieces.If one chess piece is drawn at random from the bag,the prob.of drawing a white chess piece and a black one are 2/3 and 1/3 respectively.
Bag B contains 6 white chess pieces and 8 black chess pieces.One chess piece is drawn at random from bag A and is put to Bag B,the one chess piece is drawn at random from Bag B.Find the prob.that the chess piece drawn from bag B is white.
Condition 1:
1. Drawn a white chess piece from bag A [ (2/3) ]
2. Drawn a white chess piece from bag B [ (6+1)/(6+1+8) = (7/15) ]
Condition 2:
1. Drawn a black chess piece from bag A [ (1/3) ]
2. Drawn a white chess piece from bag B [ (6)/(6+8+1) = (6/15) ]
The probability
= (2/3)(7/15) + (1/3)(6/15)
= 4/9