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 1224 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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