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

 It is currently 23 Feb 2019, 03:26

### 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

## Events & Promotions

###### Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT RC Webinar

February 23, 2019

February 23, 2019

07:00 AM PST

09:00 AM PST

Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT
• ### FREE Quant Workshop by e-GMAT!

February 24, 2019

February 24, 2019

07:00 AM PST

09:00 AM PST

Get personalized insights on how to achieve your Target Quant Score.

# A box contains 6 black balls and 4 white balls. If two balls are selec

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 53066
A box contains 6 black balls and 4 white balls. If two balls are selec  [#permalink]

### Show Tags

18 Oct 2018, 00:41
1
00:00

Difficulty:

5% (low)

Question Stats:

82% (01:02) correct 18% (01:02) wrong based on 83 sessions

### HideShow timer Statistics

A box contains 6 black balls and 4 white balls. If two balls are selected at random without replacement, what is the probability that both balls are white?

A. 7/90
B. 3/25
C. 2/15
D. 4/25
E. 4/9

_________________
Intern
Joined: 17 Dec 2016
Posts: 19
Re: A box contains 6 black balls and 4 white balls. If two balls are selec  [#permalink]

### Show Tags

18 Oct 2018, 02:06
1
Bunuel wrote:
A box contains 6 black balls and 4 white balls. If two balls are selected at random without replacement, what is the probability that both balls are white?

A. 7/90
B. 3/25
C. 2/15
D. 4/25
E. 4/9

The probability of both balls are white = 2C4/ 2C10 = 2/15

Hence, choice C is the answer
Senior Manager
Joined: 22 Feb 2018
Posts: 424
Re: A box contains 6 black balls and 4 white balls. If two balls are selec  [#permalink]

### Show Tags

18 Oct 2018, 02:57
OA:C

Probability that both ball are white$$= \frac{C(4,2)}{C(10,2)}= \frac{4!}{2!2!}*\frac{2!8!}{10!}=\frac{4*3}{2*1}*\frac{2*1}{10*9}=\frac{2}{15}$$
_________________

Good, good Let the kudos flow through you

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 4972
Location: United States (CA)
Re: A box contains 6 black balls and 4 white balls. If two balls are selec  [#permalink]

### Show Tags

19 Oct 2018, 14:25
Bunuel wrote:
A box contains 6 black balls and 4 white balls. If two balls are selected at random without replacement, what is the probability that both balls are white?

A. 7/90
B. 3/25
C. 2/15
D. 4/25
E. 4/9

There are 10 balls in the box. The probability that the first ball drawn will be white is 4/10, and the probability that the second ball will also be white is 3/9. Thus, the probability of selecting two white balls, without replacement, is 4/10 x 3/9 = 2/5 x 1/3 = 2/15.

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

CR Forum Moderator
Joined: 25 Apr 2018
Posts: 408
Re: A box contains 6 black balls and 4 white balls. If two balls are selec  [#permalink]

### Show Tags

22 Oct 2018, 01:53
Bunuel wrote:
A box contains 6 black balls and 4 white balls. If two balls are selected at random without replacement, what is the probability that both balls are white?

A. 7/90
B. 3/25
C. 2/15
D. 4/25
E. 4/9

Ways of selecting 2 white balls = 4C2
probability of selecting 2 white balls= 4C2/10C2 =2/15

_________________

Project CR Butler - 2 CR's everyday

Re: A box contains 6 black balls and 4 white balls. If two balls are selec   [#permalink] 22 Oct 2018, 01:53
Display posts from previous: Sort by