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P ( Red ) =5/10
p ( blue )=3/10
p(green)=2/10=1/5

so , p ( 2 blue , 2 red) = 5.5.3.3/10.10.10.10= 9/100

2 red and 2 blue can be arranged in 4p2 ways = 4! /2! =6 way

probability of getting 2 red and 2 blue = 6 . 9/100 = 54/400 =27/200

probability of not getting 2 red and 2 blue = (1 - 27/200 )
= 173/200

so answer is 173/200
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I set up: 1 - P(Two from red, and two from blue)

The combination of selecting two from red and two from blue:
I think of 4 vacant seats

_ _ _ _

Then there are 5 persons from red and 3 from blue, so

5 5 3 3

We have 25*9 ways to pick four persons from the red and blue teams.

However, before we place red and blue, we'll need to select the group first, selecting 2 groups (red and blue) out of 4 groups.

We got 4 choose 2 = 4!/2!2! = 6.

So, 25*9*6 is all possible arrangements.

Next, find the arrangement of four persons from the pool.

10 10 10 10

So, we have 10,000 possible arrangements.

Taken together 25*9*6/10,000 = 9*3/200

Finding the P(not from red and blue) = 1 - 27/200 = 173/200

Choice D.
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Since the question have "Exactly" so solving it in reverse
Total - (Probability of exactly 2 red and of exactly 2 blue )(total arrangement of blue and red)
= 1 - 5/10 x 5/10 x 3/10 x 3/10 x 4C2
= 1 - 27/200
= 173/200
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Total possible sequences= 10*10*10*10=10,000
Ways to choose 2 rounds out of 4 for red team = 4C2=4*3/2=6
In each 2 round, ways to select red team members = 5*5=25
In each 2 round, ways to selected blue team members= 3*3=9
Total required outcomes= 6*25*9=1,350
P(choosing exactly 2 from red team and 2 from blue team)= 1350/10000=135/1000
P(4 choices are not made up of exactly 2 from team red and 2 from team blue) = 1-(135/1000) =865/1000 =173/200

D. 173/200
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P( Not 2 Red & Not 2 Blue) = 1 - P(2 Red & 2 Blue)

Total ways of selecting = 10*10*10*10 = 10000

P(Red) = 5/10 , P( Blue) = 3/10
and Ways of Selecting red and blue is 4C2 = 6
Therefore P(2Red & 2 Blue) = 6*(5/10)*(5/10)*(3/10)*(3/10) = 27/200

Therefore Ans = 1-27/200 = 173/200
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Answer: D) 173/200

The number of ways in which we can chose 2 red and 2 blue is 4C2
The probability to choose two reds is 1/2 * 1/2
The probability to chose two blues is 3/10 * 3/10
4C2 * 1/4 * 9/100 = 54 / 400 = 27 / 200
1 - 27/200 = 173 / 200
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Question is whats the p of not choosing exactly 2 from Red and 2 from Blue.

We will find p of choosing exactly 2 reds 2 greens. P(R) = 5/10 = 1/2 P(Blue) = 3/10.

RRGG can be arranged in 4! / 2! * 2! ways = 6 ways.

6* 1/2 * 1/2 * 3/10 * 3/10 = 27/200 So P is 1-27/200 = 173/200
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Probability of Red = R = 5C1/10C1 = 5/10
Probability of Blue = B = 3/10
for Green = G = 2/10

now we don't want 2 Rs and 2 Bs,

probability of 2Rs and 2 Bs is 5/10*5/10*3/10*3/10 = 9/400
and these can be selected in following orders for each round
RBRB, RRBB, BBRR, BRBR, BRRB, RBBR = 6 ways
so 6*9/400 = 54/400

what we need is the opposite, i.e. 1-54/400 = (400 - 54)/400 = 346/400 = 173/200
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What's given in this: Total contestants = 10
R = 5
B = 3
G = 2

it is related to replacements - one can be picked again in other rounds.
And we need Probability when R = 2 and B = 2 is not the case

Use bi-junction in this to find the Probability of favorable outcomes i.e. [ 1 - unfavorable part]

Unfavorable outcomes(when exact 2 R and exactly 2 B are chosen) = 5 * 5 * 3 * 3
Total outcomes = 10 * 10 * 10 * 10
and the arrangement would also matter in unfavorable outcomes so also multiply by arrangement: 4!/ (2!2!) = 6

So the probability of unfavorable outcome would be = 6 * 25 * 9 / 100 * 10 = 27/200

Use bi-junction now: 1 - (27/200) = 173/200 OPTION D
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TARGET = 1 - P (Exactly 2R and 2B)

P(B) = 5/10 =1/2
P(R) = 3/10

P(RRBB) = (1/2) x (1/2) x (3/10) x (3/10) = 9/400

Ways of selection = RRBB, BBRR, RBRB, BRBR, BRRB, RBBR = 6

P(2R and 2B) = 9 X 6 /400 = 27/200
P(No 2R and 2B) = 1 - 27/200 = 173/200
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i am going with option d.
the probability of picking exactly 2 red and 2 blue contestants across 4 rounds = 27/200
question asks for the probability of this not happening = 1-27/200 = 179/200
a incorrect - it represents the probability of happening.
b and c incorrect - occurs when team green is ignored or selecting without replacement
e incorrect - occurs when 6 possible arrangements of chosen contestants are left out of sequence.
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At a quiz show, 10 contestants are divided into 3 teams: Team Red has 5 contestants, Team Blue has 3 contestants, and Team Green has 2 contestants.

The show has 4 rounds, and in each round, 1 contestant is chosen at random from all 10 contestants.

If a contestant chosen in one round remains eligible to be chosen again in any later round, what is the probability that the 4 choices are not made up of exactly 2 contestants from Team Red and exactly 2 contestants from Team Blue?

Total ways to select 1 contestant for each of 4 rounds = 10C1*10C1*10C1*10C1 = 10000

The number of ways to choose exactly 2 contestant from Team Read and exactly 2 contestants from Team Blue = Number of ways to select 2 rounds out of 4 * 5C1 *5C1 *3C1 *3C1 = 4C2*5*5*3*3 = 6*5*5*3*3 = 1350

The probability that the 4 choices are made up of exactly 2 contestants from Team Red and exactly 2 contestants from Team Blue = 1350/1000 = 27/200

The probability that the 4 choices are NOT made up of exactly 2 contestants from Team Read and exactly 2 contestants from Team Blue = 1 = 27/200 = 173/200

IMO D
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Bunuel
At a quiz show, 10 contestants are divided into 3 teams: Team Red has 5 contestants, Team Blue has 3 contestants, and Team Green has 2 contestants. The show has 4 rounds, and in each round, 1 contestant is chosen at random from all 10 contestants. If a contestant chosen in one round remains eligible to be chosen again in any later round, what is the probability that the 4 choices are not made up of exactly 2 contestants from Team Red and exactly 2 contestants from Team Blue?

A. 27/200
B. 1/7
C. 6/7
D. 173/200
E. 391/400


 


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Let's assume we have R R B B

Number of ways to select= 5 * 5 * 3 * 3

Number of ways to arrange = 4! / 2! * 2!

Total number of ways to select two R and two B = 5 * 5 * 3 * 3 * 4 * 3 * 2 * 1 / 2 * 2 = 5 * 5 * 3 * 3 * 3 * 2

Prob to select RRBB = 10 * 5 * 3 * 3 * 3 / 10 * 10 * 3 * 3 = 27/200

Prob to not select RRBB = 1 - 27/200 = 173/200

Option D
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Bunuel
At a quiz show, 10 contestants are divided into 3 teams: Team Red has 5 contestants, Team Blue has 3 contestants, and Team Green has 2 contestants. The show has 4 rounds, and in each round, 1 contestant is chosen at random from all 10 contestants. If a contestant chosen in one round remains eligible to be chosen again in any later round, what is the probability that the 4 choices are not made up of exactly 2 contestants from Team Red and exactly 2 contestants from Team Blue?

A. 27/200
B. 1/7
C. 6/7
D. 173/200
E. 391/400


 


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We can solve this by finding prob of complementary eveny

We can find the probability that the 4 ppl chosen are 2 from team blue , and 2 from red. The question wants to find the opposite of this , and we can simply return 1-prob(2fromBlue and 2fromRed) as the final answer.

To find out how many ways we can choose 2 from Blue and 2 from Red in 4 rounds , we can use permutation 4C2 = 6 , we can understand it like choosing 2 random spots out of 4 for ony one team , say Blue ; and then the remaining 2 spots are filled by the other team , Red here. Keep in mind the "spots here" are the chosen players in rounds.

Now , choosing 2 players from Blue has prob : 3/10 * 3/10 as there are 3 ppl in blue team , and 10 in total. And Irrespective of the round number , this probability will be same as the player pool is unchanged as the contestants can be chosen multiple times.

Similary , Prob of choosing 2 from red is 5/10*5/10 as 5 players in red.

So the total prob of choosing 2 from red and 2 from black in 4 rounds is : 6 * 9/100 * 25 *100 = 54 / 400 = 27 / 300

Final answer is 1 - prob

ANS = 1 - 27/300

= 173 / 300
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I went with (D) 173/200 on this.

We are given that there are 5 Red (R) contenstants, 3 Blue (B) contestants, 2 Yellow (Y) contestants = Total (T) 10 contestants.

Since it is a question where we have to find the probability of exactly 2 R and 2 B not being chosen, it is generally easier to find the probability of that happening and subtracting that from 1.

Now, the individual probability of R being chosen in a specific round is 5/10
The same for B is 3/10.

Since the same contestant still stays eligible for picking in subsequent round even after already being picked, we can treat it as replacement being allowed. Hence, the probability of R/B being picked still remains the same (5/10 or 3/10 respectively).

Thus, P(RRBB) = (5/10)(5/10)(3/10)(3/10) = 225/10000 = 9/400

Now, because they can be picked in any order (RRBB, BRBR, RBRB, etc.) we also need to find the number of arrangements for the case where 2 Rs and 2 Bs are selected.
Number of arrangements (RRBB) = 4! (since there are 4 elements). Also, because both R and B get repeated twice we divide 4! by 2! twice
Thus, no. of arrangements = 4!/(2!*2!) = 24/4 = 6

Thus the Total P(RRBB) = 6*9/400 = 54/400 = 27/200

Subtracting this from 1, we get the Prob. of exactly 2 R and 2 B not being picked as 1-(27/200) = 173/200
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Took me a while to understand the question, initially I was interpreting it as exactly 2 contestants from Red for ALL 4 rounds and same for Blue. Realised I was not getting anywhere so went with the following:

P(4 chosen contestants are NOT made up from exactly 2 R and 2B) = 1 - P(4 chosen contestants are made of exactly 2R and 2B)

P(R) = 5/10 = 1/2
P(B) = 3/10

P(Exactly 2R and 2B) = (No. of arrangements) x P(any one arrangement)

No. of arrangements = Choose 2 out of 4 contestants for R or B = 4C2 = 6

P(BBRR) = 3/10 x 3/10 x 1/2 x 1/2 = 9/400 (We are calculating with replacement as contestants can be repeated)

So P(2R and 2B) = 6 x 9/400 = 27/200

Required probability = 1 - 27/200 = 173/200 (D)
Bunuel
At a quiz show, 10 contestants are divided into 3 teams: Team Red has 5 contestants, Team Blue has 3 contestants, and Team Green has 2 contestants. The show has 4 rounds, and in each round, 1 contestant is chosen at random from all 10 contestants. If a contestant chosen in one round remains eligible to be chosen again in any later round, what is the probability that the 4 choices are not made up of exactly 2 contestants from Team Red and exactly 2 contestants from Team Blue?

A. 27/200
B. 1/7
C. 6/7
D. 173/200
E. 391/400


 


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Each round is independent.
Probability of choosing a red = 5/10 = 1/2
Probability of choosing a blue = 3/10

let's first find the probability of getting exactly 2 red and 2 blue selections
choose the 2 round that are red:
4C2 = 6

the probability of any one such arrangement is
(1/2)^2(3/10)^2 = 9/400
so P(exactly 2 blue and 2 red) = 6*9/400
27/200
hence required = 1 - 27/200
173/200
D
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