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.

★★★★★5.0559 reviews
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
Live EA class + 6 months of EA OnDemand
  • Expert-led weekly online sessions
  • EA Masterclass access between classes
View EA class & enroll
Limited cohort · enrollment openTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

130-point score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

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

500 ps

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 269
Joined: Sun Apr 01, 2007 5:41 am
by dunkin77 » Wed Apr 04, 2007 6:32 pm
Hi,

The answer is B)... but could anyone explain pls? thanks!


One-fifth of the light switches produced by a certain factory are defective. Four-fifths of the defective switches are rejected and 1/20 of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?

A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Sat Mar 31, 2007 11:22 am

by santy » Wed Apr 04, 2007 6:43 pm
Assume total switches = 100
1/5th of 100 switches are defective = 20
4/5th of these 20 defective switches are rejected = 16
Remaining Defective switches in the lot = (20-16) = 4
1/20th Non Defective switches rejected by mistake = 1/20 * 80 = 4
So, Non defective switches = 76
Total = Non defective + Defective switches not rejected = 76+4 = 80 are sold.
Percentage of defective switches sold = 5% (5% of 80 = 4)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 559
Joined: Tue Mar 27, 2007 1:29 amFollowed by: 2 members
Thanked: 5 times

by Cybermusings » Thu Apr 05, 2007 1:25 am
Let total number of switches produced be y. Therefore y/5 are defective. 4/5 of y/5 = 4y/25 are rejected.

y/5 - 4y/25 = y/25 of switches which are defective (but not rejected) are sold.

Total number of non-defective switches = 4y/5. Ones rejected = 1/20 of 4y/5 = 4y/100 = y/25 are rejected

Total rejected = 4y/25 + y/25 = 5y/25 = y/5. Therefore total sold = 4y/5

Therefore percent of the switches sold by the factory that are defective =( (y/25) / (4y/5) ) * 100

= 5%
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 269
Joined: Sun Apr 01, 2007 5:41 am

by dunkin77 » Thu Apr 05, 2007 8:03 am
:D very Clear - thanks!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Moderator
Posts: 772
Joined: Wed Aug 30, 2017 6:29 pmFollowed by: 6 members

by BTGmoderatorRO » Sun Oct 29, 2017 2:03 pm
Assuming 1000 light switches were produced, 200 are detectives (1/5). 160 defective and are rejected . 40 non defective were rejected mistakenly.

Also 40 defective and not rejected.
760 non defective and also not rejected
$$Total\ rejected\ and\ sold=800$$

percentage of the switches sold by the factory which are defective= $$\frac{40}{800}\cdot100=5\%$$
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8177
Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members
Location: Los Angeles, CA
Thanked: 43 times

by Scott@TargetTestPrep » Thu Nov 07, 2019 6:40 pm
dunkin77 wrote:Hi,

The answer is B)... but could anyone explain pls? thanks!


One-fifth of the light switches produced by a certain factory are defective. Four-fifths of the defective switches are rejected and 1/20 of the nondefective switches are rejected by mistake. If all the switches not rejected are sold, what percent of the switches sold by the factory are defective?

A) 4%
(B) 5%
(C) 6.25%
(D) 11%
(E) 16%

We can let the total number of switches = n

So n/5 are defective and 4n/5 are not.

4/5 x n/5 = 4n/25 defective switches are rejected. Thus 1/5 x n/5 = n/25 defective switches are not rejected and are sold.

1/20 x 4n/5 = 4n/100 = n/25 non-defective switches are rejected by mistake.

Thus, a total of 5n/25 = n/5 switches are rejected. So a total of 4n/5 switches are not rejected and are sold.

So the percent of the switches sold that are defective is:

(n/25)/(4n/5) = 5n/(100n) = 1/20 = 5%

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1