A computer chip manufacturer expects the ratio of the number

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BTGmoderatorLU: Moderator; Posts: 2598; Joined: Sun Oct 15, 2017 1:50 pmFollowed by: 6 members

by BTGmoderatorLU » Mon Feb 11, 2019 3:18 pm

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Source: GMAT Prep

Shipment ------No. of Defective Chips/shipment---Total Chips in shipment
S1 ------------------------------- 2 ------------------------------------5000
S2 ------------------------------- 5 -------------- --------------------12000
S3 ------------------------------- 6 ---------------------------------- 18000
S4 ------------------------------- 4 ---------------------------------- 16000

A computer chip manufacturer expects the ratio of the number of defective chips to be the total number of chips in all future shipments equal to the corresponding ratio for shipments S1, S2, S3, and S4 combined as shown in the table above. What is the expected number of defective chips in a shipment of 60000 chips?

A. 14
B. 20
C. 22
D. 24
E. 25

The OA is B

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Source: Beat The GMAT — Problem Solving | Mon Feb 11, 2019 3:18 pm

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Brent@GMATPrepNow: GMAT Instructor; Posts: 16207; Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members; Location: Vancouver, BC; Thanked: 5254 times; GMAT Score:770

by Brent@GMATPrepNow » Mon Feb 11, 2019 3:30 pm

BTGmoderatorLU wrote:Source: GMAT Prep

Shipment ------No. of Defective Chips/shipment---Total Chips in shipment
S1 ------------------------------- 2 ------------------------------------5000
S2 ------------------------------- 5 -------------- --------------------12000
S3 ------------------------------- 6 ---------------------------------- 18000
S4 ------------------------------- 4 ---------------------------------- 16000

A computer chip manufacturer expects the ratio of the number of defective chips to be the total number of chips in all future shipments equal to the corresponding ratio for shipments S1, S2, S3, and S4 combined as shown in the table above. What is the expected number of defective chips in a shipment of 60000 chips?

A. 14
B. 20
C. 22
D. 24
E. 25

The OA is B

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

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Scott@TargetTestPrep: GMAT Instructor; Posts: 8196; Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members; Location: Los Angeles, CA; Thanked: 43 times

by Scott@TargetTestPrep » Wed Feb 13, 2019 6:35 pm

BTGmoderatorLU wrote:Source: GMAT Prep

Shipment ------No. of Defective Chips/shipment---Total Chips in shipment
S1 ------------------------------- 2 ------------------------------------5000
S2 ------------------------------- 5 -------------- --------------------12000
S3 ------------------------------- 6 ---------------------------------- 18000
S4 ------------------------------- 4 ---------------------------------- 16000

A computer chip manufacturer expects the ratio of the number of defective chips to be the total number of chips in all future shipments equal to the corresponding ratio for shipments S1, S2, S3, and S4 combined as shown in the table above. What is the expected number of defective chips in a shipment of 60000 chips?

A. 14
B. 20
C. 22
D. 24
E. 25

The OA is B

We are given the following:

S1: 2 defective chips out of 5,000 total

S2: 5 defective chips out of 12,000 total

S3: 6 defective chips out of 18,000 total

S4: 4 defective chips out of 16,000 total

The ratio of the number of defective chips to total chips is:

(2 + 5 + 6 + 4)/(5,000 + 12,000 + 18,000 + 16,000)

17/51,000 = 1/3,000

We see that we would expect 1 chip out of every 3,000 chips to be defective.

We can set up a proportion to determine, x, the number of defective chips, that we would expect in a shipment of 60,000 chips.

1/3,000 = x/60,000

60,000 = 3,000x

x = 20

Answer: B

Scott Woodbury-Stewart
Founder and CEO
[email protected]

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