Six machines, each working at the same constant rate

[sachin.w]

Here's how I solved it:

6 machines complete a job J in 12 days

so

6 machines complete 1/12 J job in 1 day

=>

1 machine completes 1/72 J job in 1 day
=>
1 machine completes 8/72 J job in 8 days
=>
so to complete J job in 8 days,
9 machines are needed: (8/72)*9 J=J

you already have 6 machines, you need 3 more machines ..

[RonPurewal]

Here's how I solved it:

6 machines complete a job J in 12 days

so

6 machines complete 1/12 J job in 1 day

=>

1 machine completes 1/72 J job in 1 day
=>
1 machine completes 8/72 J job in 8 days
=>
so to complete J job in 8 days,
9 machines are needed: (8/72)*9 J=J

you already have 6 machines, you need 3 more machines ..

yes, this works (and is quite similar to the solution in the immediately preceding post).

[mehulchavada]

also 6 machines - 12 days
i.e Rate for 6 machines= 1 job/12
now we want to find x machines for having rate= 1 job/8
i.e (1/8*6)/1/12 = 9
finally 9-6=3.

[tim]

thanks!

[muktavpatil]

Hi,
This is how I worked it out.
If 6 machines complete the job in 12 days
Then 1 machine will take 6*12 = 72 days to complete the same job. So, how many machines will be required to do the job in 8 days?
72/8 = 9 machines
Additional Machines needed = 9-6 = 3

[RonPurewal]

That works too.