I want to know if I did this right.
six machines working at a 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?
ans 3
6/x = x/8 cross multiply and get 3
is this correct?
rates
This topic has expert replies
- jayhawk2001
- Community Manager
- Posts: 789
- Joined: Sun Jan 28, 2007 3:51 pm
- Location: Silicon valley, California
- Thanked: 30 times
- Followed by:1 members
Use the standard rate-formula to solve this
6 machines complete the job in 12 days, so
6 * 1/x = 1/12, so x = 72
n additional machines complete the job in 8 days
(n+6) * 1/72 = 1/8
So, n = 3
6 machines complete the job in 12 days, so
6 * 1/x = 1/12, so x = 72
n additional machines complete the job in 8 days
(n+6) * 1/72 = 1/8
So, n = 3
GMAT/MBA Expert
- Scott@TargetTestPrep
- GMAT Instructor
- Posts: 7223
- Joined: Sat Apr 25, 2015 10:56 am
- Location: Los Angeles, CA
- Thanked: 43 times
- Followed by:29 members
We are given that six machines, each working at the same constant rate, together can complete a certain job in 12 days. Since rate = work/time and if we consider work as 1, the rate of the six machines is 1/12.yvonne12 wrote:
six machines working at a 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?
We need to determine how many additional machines, each working at the same constant rate, will be needed to complete the same job in 8 days. In other words we need to determine how many additional machines are needed to work at a rate of 1/8. Since each machine works at the same constant rate, we can use a proportion to first determine the number of machines needed to work at the rate of 1/8.
Our proportion is as follows: 6 machines is to a rate of 1/12 as x machines is to a rate of 1/8.
6/(1/12) = x/(1/8)
72 = 8x
x = 9
So we need 9 - 6 = 3 more machines.
Answer: 3
Scott Woodbury-Stewart
Founder and CEO
[email protected]
See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews