Running at the same constant rate, a identical machines

Question

Running at the same constant rate, a identical machines can produce a total of 120 bolts per minute. At this rate, how many bolts could 4 such machines produce in 5 minutes?

(A) a/6
(B) a/600
(C) 150/a
(D) 480/a
(E) 2,400/a

sashiim20 · Answer

"a" identical machines can produce 120 bolts per minute. 
In 5 mins "a" machines can produce = 120 x 5 = 600 bolts

Therefore number of bolts produced by 4 such machines =  \frac{600 * 4}{a}  =  \frac{2400}{a} 
Answer E...

amanvermagmat · Answer

'a' machines in 1 minute = 120 bolts
'a' machines in 4 minutes = 5*120 = 600 bolts

This is a direct variation between number of bolts and number of machines. (greater the number of machines, greater the number of bolts produced)
Let bolts produced by 4 such machines be 'x'

So we have a/4 = 600/x Or x = 2400/a

Hence  E answer

generis · Answer

1. Find INDIVIDUAL RATE:

W / (# of workers * time) = individual rate

120 / a*1 = 120/a

2. How many bolts produced by 4 machines in 5 minutes?

Find TOTAL WORK given new # of machines and new time:

(# of workers) * (individual rate) * (time) = total work

4 * 120/a * 5 = 2400/a

Answer E

EMPOWERgmatRichC · Answer

Hi rohan2345,

This question can be solved by TESTing VALUES.

We're told that a total of A machines (working together) will produce 120 bolts/minute. We're asked for the number of bolts that could be produced by 4 of these machines in 5 minutes.

IF... A=2
Then 2 machines will produce those 120 total bolts/minute. Thus....
4 machines will produce 240 bolts/minute. 
In 5 minutes, those 4 machines will produce (5)(240) = 1200 bolts

So we're looking for an answer that equals 1200 when A=2. There's only one answer that 'fits'...

Final Answer:  E

GMAT assassins aren't born, they're made,
Rich

Bunuel · Answer

______________________
Edited the tags. Thank you.

GmatDM2016 · Answer

easier to get confused without the appropriate highlight in the question part -
Running at the same constant rate,  a  identical machines can produce a total of 120 bolts per minute.

a machines -> 120 
1 machine -> 120/a
4 machines -> (120*4)/a

above is all per minute, so for 5 minutes - 
(120*4*5)/a = 2400/a

E

JeffTargetTestPrep · Answer

We are given that the rate of a machines is 120. Thus, the rate of 4 machines is:

a/120 = 4/x

ax = 480

x = 480/a

Since the rate of 4 machines is 480/a bolts per minute, 4 machines can produce 480/a * 5 = 2400/a bolts in 5 minutes.

Answer: E

bumpbot · Answer

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Running at the same constant rate, a identical machines

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