proportion question type

[hutch27]

Each employee of company X works in exactly one of the departments G and H. Currently, there are 1,500 employees at company X and 60 percent of the employees at company X work in department G. If every employee currently at company X remains at company X and remains in the department they are in, then what is the number of new employees who must be hired to work in department G so that 85 percent of the employees working in company X work in department G?

1,275
1,700
2,500
3,750
4,000

oa is C

so this is a kaplan question but their explanation is horrendous. I got this one wrong but it was b/c of a careless error I still dont really understand.. thats why im posting it

this is what i did..

x/85= 600/15 <-- i just assumed since 600 is the constant part I can make that = to 15% and let x = the part for the remaning 85%

i got x=3400 and then i added 600 and picked E... obviously wrong. but i still dont know why i should subtract the 2. was it my method (ie is there an easier way)?

[GMATGuruNY]

Each employee of company X works in exactly one of the departments G and H. Currently, there are 1,500 employees at company X and 60 percent of the employees at company X work in department G. If every employee currently at company X remains at company X and remains in the department they are in, then what is the number of new employees who must be hired to work in department G so that 85 percent of the employees working in company X work in department G?

1,275
1,700
2,500
3,750
4,000

oa is C

Work with the value that DOESN'T CHANGE: the number of employees in Department H.

Since 60% of the 1500 employees work in Department G, 40% work in Department H:
.4(1500) = 600.
After more employees are hired, the 600 employees in Department H must constitute 15% of the total number of employees:
600 = .15x
x = 600/.15 = 60000/15 = 4000.
Thus:
Number of employees hired = new total - old total = 4000-1500 = 2500.

The correct answer is C.

[hutch27]

ah, got it. Forgot the question was asking about number of new employees hired..