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.
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
Ratios
This topic has expert replies
-
singhmaharaj
- Senior | Next Rank: 100 Posts
- Posts: 38
- Joined: Tue Feb 10, 2009 6:24 am
- Location: Hong Kong
- Followed by:2 members
GMAT/MBA Expert
-
Brent@GMATPrepNow
- 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
Let's find some TOTALS for all 4 shipments combined.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
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
-
singhmaharaj
- Senior | Next Rank: 100 Posts
- Posts: 38
- Joined: Tue Feb 10, 2009 6:24 am
- Location: Hong Kong
- Followed by:2 members
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??? :!:
:
# 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??? :!:
:GMAT/MBA Expert
-
Brent@GMATPrepNow
- 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
Perhaps the question is somewhat ambiguous.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??? :!:
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
