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Re: Working at the same constant rate, 4 machines, [#permalink]
Libra wrote:
If it takes 4 machines 8 days to make 16 birdhouses, this means that it takes 1 machine 2 days to make 4 birdhouses, correct? Just divide everything by 4.

So we have 1 machine = 2 days = 4 houses. How many are required to make 64 houses in 16 days? The numbers just don't add up. In 16 days, 8 machines can make 32 houses only, NOT 64. Throw the question out.


No, not correct.

this means that it takes 1 machine 2 days to make 4 birdhouses, correct? Just divide everything by 4.
If it were the case that it takes 1 machine 2 days to make 4 birdhouses, then that would mean 1 machine can make 2 bird houses every 1 day
This would mean that 1 machine can make 16 bird houses every 8 days.
HOWEVER, the question tells us that it takes 4 machines 8 days to make 16 birdhouses.
So your conclusion must be incorrect.
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Re: Working at the same constant rate, 4 machines, [#permalink]
Use:

M1 x T1 x W2 = M2 x T2 x W1
4 x 8 x 64 = M2 x 16 x 16
M2 = 8

Hence, option C
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Re: Working at the same constant rate, 4 machines, [#permalink]
If 4 machines, can make a total of 2 birdhouses, then 1 machine can make 2/4= 0.5 birdhouses per machine right. Using this approach I arrive at a different answer.

GreenlightTestPrep wrote:
GreenlightTestPrep wrote:
Working at the same constant rate, 4 machines, working together, take 8 days to make a total of 16 birdhouses.
How many such machines are required to make 64 birdhouses in 16 days?
A) 2
B) 4
C) 8
D) 16
E) 32


4 machines take 8 days to make 16 birdhouses.
So, in ONE DAY, the 4 machines, can make a total of 2 birdhouses
So, in 16 days, those same 4 machines can make 32 birdhouses
So, if we add an additional 4 machines (that can also make 32 birdhouses in 16 days), the 8 combined machines will make 64 birdhouses in 16 days.

Answer: C
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Re: Working at the same constant rate, 4 machines, [#permalink]
Chaithraln2499 wrote:
If 4 machines, can make a total of 2 birdhouses, then 1 machine can make 2/4= 0.5 birdhouses per machine right. Using this approach I arrive at a different answer.


Your conclusion is correct. However, I need to see the rest of your solution.
I'll get you started...

4 machines take 8 days to make 16 birdhouses.
So, in ONE DAY, the 4 machines, can make a total of 2 birdhouses
So, in ONE DAY, the ONE machine, can make a total of 0.5 birdhouses

Please show me the rest of your solution
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Re: Working at the same constant rate, 4 machines, [#permalink]
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