A jar contains only x black balls and y white balls

tejal777 · **Posted:** Sat Jun 06, 2009 4:54 am


		00:00



	GMAT Timer...

A jar contains only x black balls and y white balls. One ball is drawn randomly from the jar and is not replaced. A second ball is then drawn randomly from the jar. What is the probability that the first ball drawn is black and the second ball drawn is white?

A. \frac{x}{x+y}*\frac{y}{x+y}

B. \frac{x}{x+y}*\frac{x-1}{x+y-1}

C. \frac{xy}{x+y}

D. \frac{x-1}{x+y}*\frac{y-1}{x+y}

E. \frac{x}{x+y}*\frac{y}{x+y-1}

[Reveal] Spoiler: OA

E

humans · **Posted:** Sat Jun 06, 2009 9:09 am

Black balls = x
White balls = y

Total no of balls = x + y

Probability of first ball drawn is black = x/(x+y)
As the ball is not replaced now the total remaining balls = (x+y-1)

Probability of second ball drawn is white = y/(x+y-1)

Total probability = [\frac{x}{(x+y)}]*[\frac{y}{(x+y-1)}]

Baten80 · **Posted:** Tue Jan 10, 2012 7:18 am

From 1000ps section 21-13.

metallicafan · **Posted:** Tue Feb 21, 2012 2:02 pm

It seems difficult, but actually is one of the easiest.
Just do it.

\frac{x}{(x+y)} * \frac{y}{(x+y-1)}

+1 E

Similar topics	Author	Replies	Views	Last post
white Balls / Black Balls in GMAT Math Questions and Intellectual Discussions	araspai	4	385	Thu Oct 09, 2003 9:11 pm
Black/White balls arrangements in GMAT Math Questions and Intellectual Discussions	qhoc0010	2	216	Mon Dec 27, 2004 2:12 pm
3) There are 12 white balls and 12 black balls that are in GMAT Problem Solving (PS)	Praetorian	3	235	Sun Oct 12, 2003 9:13 pm
Q1. A bag contains 3 red,6 white n 7 black balls.2 balls are in GMAT Problem Solving (PS)	alfa_beta01	5	330	Thu Jun 01, 2006 11:25 am
The probability of pulling a black ball out of a glass jar in GMAT Problem Solving (PS)	sperumba	6	292	Thu Jan 26, 2006 6:17 pm

A jar contains only x black balls and y white balls

Who is online

Main Navigation

GMAT Resources

Partners

MBA Resources