GMAT Prep Question - Work / Rates

This topic has expert replies
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Mon Mar 09, 2009 12:22 pm

GMAT Prep Question - Work / Rates

by werdwerd » Mon Mar 09, 2009 12:24 pm
Six machines, each working at the same constant rate, together can complete a certain job in 12 days. How many additional machines, each working at the same constant rate, will be needed to complete the job in 8 days?

This question is off of the GMAT Prep test I took.

Can someone please walk me through this one? I think I'm getting thrown off because there's 6 individual units working, rather than 1 and another, i'm going in circles in my head. Thank you!
Source: — Problem Solving |

Junior | Next Rank: 30 Posts
Posts: 16
Joined: Mon Mar 09, 2009 10:56 am

by keeyu2 » Mon Mar 09, 2009 12:38 pm
6 machines = 12 days

set 1/6 ( = 1 machine ) = 12 days.
1 machine = 72 days.

9 machines = 8 days

I think.

Newbie | Next Rank: 10 Posts
Posts: 8
Joined: Fri Feb 27, 2009 6:25 pm

by ML » Tue Mar 10, 2009 6:18 am
additional machines so 9-6=3 machines

Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Mon Mar 09, 2009 12:22 pm

by werdwerd » Tue Mar 10, 2009 5:32 pm
perfect - thank you!