It is currently 11 Dec 2017, 04:27

### 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 June
Open Detailed Calendar

# One-fifth of the light switches produced by a certain

Author Message
Senior Manager
Joined: 13 Mar 2007
Posts: 293

Kudos [?]: 59 [0], given: 0

Location: Russia, Moscow
One-fifth of the light switches produced by a certain [#permalink]

### Show Tags

29 Mar 2007, 06:19
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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%

Kudos [?]: 59 [0], given: 0

Manager
Joined: 02 Jan 2007
Posts: 208

Kudos [?]: 11 [0], given: 0

### Show Tags

29 Mar 2007, 10:40
I go with B.

let the total no. of switches = 100
so defective (or lets say d) = 20
of these 4/5 get rejected, so
& nrd (non-rejected defectives) =4 (20-16 ie 4/5 of 20)..........i

Total Non-defective switches (or n) = 80
1/20 of these are rejected by mistake, thats
mr (mistakenly rejected) = 4
so good switches sold = 76........................ii

With this we now we need to find out how many switches sold
and how many rejectes sold.

Total sold = 80 (adding i & ii)
of these defective = 4 ......from i

4/80*100 = 5%

Kudos [?]: 11 [0], given: 0

Intern
Joined: 11 Feb 2007
Posts: 30

Kudos [?]: 2 [0], given: 0

### Show Tags

29 Mar 2007, 11:51
i get 5% too. good explanation.

Kudos [?]: 2 [0], given: 0

Manager
Joined: 28 Feb 2007
Posts: 195

Kudos [?]: 12 [0], given: 0

Location: California

### Show Tags

29 Mar 2007, 20:43
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%

Rejected defective switches = 1/5 x 4/5 = 4/25
Accepted defective swicthes = 1/5 x 1/5 = 1/25

Rejected good switches = 4/5 x 1/20 = 1/25
Accepted good switched = 4/5 x 19/20 = 19/25

Since all accepted switches are sold so total switches sold = 1/25 + 19/25 = 4/5

required answer = 1/25 / 4/5 = 1/20 = 5%

Kudos [?]: 12 [0], given: 0

Senior Manager
Joined: 13 Mar 2007
Posts: 293

Kudos [?]: 59 [0], given: 0

Location: Russia, Moscow

### Show Tags

29 Mar 2007, 23:19

Kudos [?]: 59 [0], given: 0

GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5032

Kudos [?]: 456 [0], given: 0

Location: Singapore

### Show Tags

30 Mar 2007, 00:51
Assume total 100 switches produced.

(100)*(1/5) = 20 switches are defective

4/5*(20) = 16 swtitches are rejected

1/20*(80) = 4 switches are rejected by mistake.

# of switches sold = 76 + 4 = 80
# of defects sold = 4
% = 4/80 * 100% = 5%

Kudos [?]: 456 [0], given: 0

30 Mar 2007, 00:51
Display posts from previous: Sort by

# One-fifth of the light switches produced by a certain

Moderator: chetan2u

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.