There are 6 red balls and 4 blue balls in a jar. If 2 balls are select

Question

There are 6 red balls and 4 blue balls in a jar. If 2 balls are selected from the jar, what is the probability that 2 balls selected are red balls?

A. 1/10 
B. 1/9 
C. 3/10 
D. 3/15 
E. 2/15

chetan2u · Answer

Hi,

6 red balls can be collected in 6*5 ways..
All 10 balls can be picked in 10*9 ways..
So PROBABILITY=  \frac{6*5}{10*9}=1/3 ..
However the answer is not there..

So your Q is wrong or there is a typo in which you are looking for PROBABILITY of picking blue balls..
Now answer will be  \frac{4*3}{10*9}=2/15 
Ans E...

Pl EDIT your Q accordingly

BrentGMATPrepNow · Answer

Chetan's solution uses  counting methods .

Here's a solution that uses  probability rules :

P(both balls are red) = P(1st ball is red   AND   2nd ball is red)
= P(1st ball is red)   x   P(2nd ball is red)
= 6/10   x   5/9
= 1/3

sashiim20 · Answer

I am getting a different answer which is not in options.
Here is the method i solved.
Total number of balls = 10
Total red balls = 6. Total Blue balls = 4
Need to select 2 balls from 10.
Probability of 2 balls selected are red = Selecting 1st red ball out of 10 x Selecting 2nd red ball out of 9
 \frac{6}{10}  x  \frac{5}{9}  =   \frac{1}{3}

Another method;
Selecting 2 red balls from total 6 red balls = 6C2 =  \frac{6*5}{2}  = 15
Selecting 2 balls from total 10 balls = 10C2 =  \frac{10*9}{2}  = 45
 \frac{6C2}{10C2}  =  \frac{15}{45}  =   \frac{1}{3}

Answer   \frac{1}{3}

MathRevolution · Answer

==> You get 4C2/10C2==2/15. The answer is E.

Answer: E

Bunuel · Answer

As pointed out several times above the answer must be 1/3. For the answer to be 2/15 the question should asks about the probability of two BLUE balls, not red.,

ScottTargetTestPrep · Answer

The probability that two red balls are selected is:

6/10 x 5/9 = 30/90 = 1/3

There are 6 red balls and 4 blue balls in a jar. If 2 balls are select

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There are 6 red balls and 4 blue balls in a jar. If 2 balls are select

Prep Toolkit

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