GMATinsight wrote:

In a workshop, 10 machines working simultaneously can finish a work of manufacturing 3000 components in 10 days while working 9 hours a day. What is the minimum number of additional machines required at the same workshop to finish the work of manufacturing 5000 similar components if work needs to be delivered in 6 days and maximum number of hours that machines can operate in a day is 10?

A) 4

B) 5

C) 10

D) 15

E) 25

SOURCE:

http://www.GMATinsight.comNice question! For these questions, I almost always find the individual machine or worker rate, using a slightly changed version of the RTW table. Just add one column for "Number of workers/machines," and it's easy:

Attachment:

Revised Work Formula Table.jpg [ 40.42 KiB | Viewed 1202 times ]
Revised formula: (

# of workers)*(rate)*(time) = Work

In this case, you have to use

HOURS for units of

time.Calculate first row: 10 days * 9 hrs/day = 90 hours total

Calculate second row: 6 days * 10 hrs/day = 60 hours total

1. Find individual machine rate ==>

(10)*

(R)*(90) = 3000

R = \(\frac{3000}{900}\) =

\(\frac{10}{3}\)2. Use that rate in second row to find TOTAL number of machines needed for new task ==>

(# of machines TOTAL)*(\(\frac{10}{3}\))*(60) = 5000

# of machines = \(\frac{5000}{200}\) =

25 TOTAL

Question asks, how many

more machines needed for new task. 25 (need) - 10 (have) = 15.

Answer

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