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

Redeem

Ratios

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Senior | Next Rank: 100 Posts
Posts: 38
Joined: Tue Feb 10, 2009 6:24 am
Location: Hong Kong
Followed by:2 members

Ratios

by singhmaharaj » Tue May 06, 2014 2:14 am
Shipment Number of Defective Chips in the Shipment Total number of Chips in the Shipment
S1 2 5,000
S2 5 12,000
S3 6 18,000
S4 4 16,000

A computer chip manufacturer expects the ratio of the number of defective chips to the total number of chips in all the future shipments to equal the corresponding rate for shipments S1, S2, S3, and S4 combined, as shown in the table above. What is the expected number of defective chips in the shipment of 60,000 chips?

A) 14

B) 20

C) 22

D) 24

E) 25

My answer matches none of the choices. I calculated the answer as 84.
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Tue May 06, 2014 3:25 am
singhmaharaj wrote:Shipment / Number of Defective Chips in the Shipment / Total number of Chips in the Shipment
S1 / 2 / 5,000
S2 / 5 / 12,000
S3 / 6 / 18,000
S4 / 4 / 16,000

A computer chip manufacturer expects the ratio of the number of defective chips to the total number of chips in all the future shipments to equal the corresponding rate for shipments S1, S2, S3, and S4 combined, as shown in the table above. What is the expected number of defective chips in the shipment of 60,000 chips?

A) 14

B) 20

C) 22

D) 24

E) 25
Let's find some TOTALS for all 4 shipments combined.
There are 51,000 chips altogether
There are 17 defective chips altogether.

So, 17/51000 of the chips are defective. (notice that 17 divides nicely into 51000!)
SIMPLIFY: 1/3000 of the chips are defective

So, if we have a shipment of 60,000 chips, 1/3000 of them will be defective.
(1/3000)(60,000) = 20 defective chips

Answer: B

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
Senior | Next Rank: 100 Posts
Posts: 38
Joined: Tue Feb 10, 2009 6:24 am
Location: Hong Kong
Followed by:2 members

by singhmaharaj » Tue May 06, 2014 5:44 am
Since the question said that the total number of chips in all future shipments to equal the corresponding rate for the shipment S1, S2, S3, and S4 combined, my interpretation was something like this

# of defective / 60,000 = { (2/5000) + (5/12,000) + (6/18,000) + (4/16,000) }

# of defective /60,000 = 1/1000 { 2/5 + 5/12 + 6/18 + 4/16}

# of defective /60,000 = 1/1000 {(12 + 25 + 20 + 15)} / 60

# of defective = 84

This does not match any of the given answer choices.

But I want to understand why am I wrong??? :!: :?:
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Tue May 06, 2014 10:48 am
singhmaharaj wrote:Since the question said that the total number of chips in all future shipments to equal the corresponding rate for the shipment S1, S2, S3, and S4 combined, my interpretation was something like this

# of defective / 60,000 = { (2/5000) + (5/12,000) + (6/18,000) + (4/16,000) }

# of defective /60,000 = 1/1000 { 2/5 + 5/12 + 6/18 + 4/16}

# of defective /60,000 = 1/1000 {(12 + 25 + 20 + 15)} / 60

# of defective = 84

This does not match any of the given answer choices.

But I want to understand why am I wrong??? :!: :?:
Perhaps the question is somewhat ambiguous.
What does it mean to say the "corresponding rate for shipments S1, S2, S3, and S4 combined"?

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Post new topic Post Reply
• Page 1 of 1