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

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0563 reviews
Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep
NEWSWEEK READERS’ CHOICE AWARDS 2026

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

GMATLiveTeach Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

How do I solve this question?

Data Sufficiency, Multi-Source Reasoning, Table Analysis, Graphics Interpretation, Two-Part Analysis
Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
User avatar
Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Tue Mar 29, 2016 4:42 pm
by Taiana Melo » Tue Mar 29, 2016 4:52 pm
ÃŒf a quality control check is made by inspecting a sample of 2 lightbulbs from a box of 12 lightbulbs, how many different samples can be chosen?
6
24
36
66
72
Top
Join the discussion
Source: — Data Insights |

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members
Location: Palo Alto, CA
Thanked: 2867 times
GMAT Score:800

How do I solve this question?

by [email protected] » Tue Mar 29, 2016 9:32 pm
Hi Taiana Melo,

This looks like a PS question (not an IR question), so you should have posted it here:

https://www.beatthegmat.com/problem-solving-f6.html

That having been said, I'll be happy to walk you through it. This is an example of a straight-forward Combinations question. When dealing with Combinations, it often helps to use the Combination Formula:

N! / K!(N-K)! where N is the total number of items and K is the number in the 'sub-group'

Here, we have 12 lightbulbs and we're choosing groups of 2. Since it doesn't matter which lightbulb comes first (choosing bulb A and then bulb B is the SAME as choosing bulb B and then bulb A), the order of the bulbs does NOT matter. THAT is a big 'clue' to use the Combination Formula:

12! / 2!(12-2)! = 12! / 2!10! = (12)(11) / (2)(1) = 132/2 = 66

Final Answer: B

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
Join the discussion
User avatar
Legendary Member
Posts: 2135
Joined: Mon Feb 03, 2014 9:26 amFollowed by: 140 members
Location: https://martymurraycoaching.com/
Thanked: 955 times
GMAT Score:800

by MartyMurray » Tue Mar 29, 2016 9:40 pm
You are selecting two lightbulbs out of 12.

The first bulb is any one of 12.

The second bulb is one of the remaining 11.

So there are 12 choices for the first bulb and for every 12 there are 11 choices for the second bulb. Therefore your next step is to multiply 12 x 11 to get 132.

However, 132 is not the correct answer as it contains samples picked twice in opposite ways.

For instance, you could have picked bulb 1 first and bulb 2 second.

Alternatively, you could have picked bulb 2 first and bulb 1 second.

Those two sets of choices would produce the same sample. So you need to account for the fact that the same two bulbs can be chosen in two different orders.

That is done by dividing (12 x 11)/2! = 132/2 = 66.

The correct answer is D.
Marty Murray
Perfect Scoring Tutor With Over a Decade of Experience
MartyMurrayCoaching.com
Contact me at [email protected] for a free consultation.
Top
Join the discussion