marbles left in the jar are red

BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

This topic has expert replies

Post new topic Post Reply

Previous Topic Next Topic

sanju09: GMAT Instructor; Posts: 3650; Joined: Wed Jan 21, 2009 4:27 am; Location: India; Thanked: 267 times; Followed by:80 members; GMAT Score:760

marbles left in the jar are red

by sanju09 » Fri Sep 17, 2010 2:23 am

A jar contains 30 marbles, of which 20 are red and 10 are blue. If 9 of the marbles are removed, how many of the marbles left in the jar are red?

[1] Of the marbles removed, the ratio of the number of red ones to the number of blue ones is 2:1.

[2] Of the first 6 marbles removed, 4 are red.

[spoiler]Source: www.avenuesabroad.org[/spoiler]

The mind is everything. What you think you become. -Lord Buddha

Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001

www.manyagroup.com

Quote

Source: Beat The GMAT — Data Sufficiency | Fri Sep 17, 2010 2:23 am

GMAT/MBA Expert

Rahul@gurome: GMAT Instructor; Posts: 1179; Joined: Sun Apr 11, 2010 9:07 pm; Location: Milpitas, CA; Thanked: 447 times; Followed by:88 members

by Rahul@gurome » Fri Sep 17, 2010 4:28 am

(1) Number of red marbles : Number of blue marbles = 2:1 implies number of red marbles removed = 2* number of blue marbles removed.
If x blue marbles are removed, then x + 2x = 9 implies x = 3
Since 9 marbles are removed so, number of red marbles removed = 2*3 = 6
Therefore, number of red marbles left in the jar = 20 - 6 = 14
So, (1) is SUFFICIENT.

(2) This statement tells us that out of the first 6 marbles, 4 were red marbles but there is no info on the remaining 3 marbles that were removed.
So, (2) is NOT SUFFICIENT.

The correct answer is [spoiler](A)[/spoiler].

Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)

Quote

GMAT/MBA Expert

Scott@TargetTestPrep: GMAT Instructor; Posts: 8086; Joined: Sat Apr 25, 2015 10:56 am; Location: Los Angeles, CA; Thanked: 43 times; Followed by:29 members

by Scott@TargetTestPrep » Wed Dec 13, 2017 1:00 pm

sanju09 wrote:A jar contains 30 marbles, of which 20 are red and 10 are blue. If 9 of the marbles are removed, how many of the marbles left in the jar are red?

[1] Of the marbles removed, the ratio of the number of red ones to the number of blue ones is 2:1.

[2] Of the first 6 marbles removed, 4 are red.

We are given that a jar contains 30 marbles, of which 20 are red and 10 are blue. We are also given that 9 marbles are removed, and we need to determine the number of red marbles left in the jar.

Statement One Alone:

Of the marbles removed, the ratio of the number of red ones to the number of blue ones is 2:1.

We can re-express the ratio of red to blue marbles removed as 2x : x and solve the equation:

2x + x = 9

3x = 9

x = 3

From this we see that 6 red marbles and 3 blue marbles are removed. Thus there are 14 red marbles left in the jar. Statement one alone is sufficient to answer the question.

Statement Two Alone:

Of the first 6 marbles removed, 4 are red.

From this we know that at least 4 red marbles and 2 blue marbles are removed. However, since we don't know how many of the last 3 marbles are red (or blue), we can't determine the number of red marbles left in the jar. For example, if the last 3 marbles removed are all red, then 7 red marbles are removed, and thus there are 13 red marbles left in the jar. However, if none of the last 3 marbles are red, then only 4 red marbles are removed, and thus there are 16 red marbles left in the jar. Statement two alone is not sufficient to answer the question.

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]