GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 06 Dec 2019, 05:28

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# In a jar, 9 balls are white and the rest are red. If two balls are to

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 59574
In a jar, 9 balls are white and the rest are red. If two balls are to  [#permalink]

### Show Tags

02 Oct 2018, 02:34
00:00

Difficulty:

35% (medium)

Question Stats:

78% (02:52) correct 22% (01:52) wrong based on 41 sessions

### HideShow timer Statistics

In a jar, 9 balls are white and the rest are red. If two balls are to be chosen at random from the jar without replacement, the probability that the balls chosen will both be white is 6/11. What is the number of balls in the jar?

(A) 10
(B) 11
(C) 12
(D) 13
(E) 15

_________________
Manager
Joined: 21 Nov 2016
Posts: 71
GMAT 1: 640 Q47 V31
Re: In a jar, 9 balls are white and the rest are red. If two balls are to  [#permalink]

### Show Tags

02 Oct 2018, 03:44
2
The jar has 9 white balls, and the rest are red balls.
So, let total balls = t
The probability of picking 2 white balls without replacement is = 6/11
So, (9/t)x(8/t-1) = 6/11
on simplifying the above equation we would get a quadratic equation of the form,
t^2-t-132=0
Further simplifying we would get,
(t-12)(t+11)=0
Implies, t = 12, or t = -11
Since the no. of balls is supposed to be a positive integer, so t =12
So, the correct answer is C.
Re: In a jar, 9 balls are white and the rest are red. If two balls are to   [#permalink] 02 Oct 2018, 03:44
Display posts from previous: Sort by