GMATPrep question on DS - average
This topic has expert replies
Source: Beat The GMAT — Data Sufficiency |
-
jackcrystal
- Senior | Next Rank: 100 Posts
- Posts: 31
- Joined: Mon Aug 04, 2008 2:04 pm
- Thanked: 1 times
-
cramya
- Legendary Member
- Posts: 2467
- Joined: Thu Aug 28, 2008 6:14 pm
- Thanked: 331 times
- Followed by:11 members
M- NO OF MANAGER
D- NO OF DIRECTORS
E-NO OF EMPLOYEES
Let MAVG be managers avg salary
Let EMPAVG be employees average slaary
Let DIREAVG be directors avg salary
FORMAULA IS : (MAVG*M + DIRAVG*D) / M+D = EMPAVG (1)
To find ratio of M/D from which we can find the percent by multipying by 100
Stmt I
MAVG = EMPAVG-5000 (2)
cant find ratio m/n with this
INSUFF
Stmt II
DAVG = EMPAVG+15000 (3)
cant find ratio m/n with this
INSUFF
Stmt I and II together
Substitute in (1),
MAVG = EMPAVG-5000 FROM (2) AND DAVG = EMPAVG+15000 (3)
(MAVG*M + DIRAVG*D) / M+D = EMPAVG
= ((EMPAVG-5000)*M + (EMPAVG+15000)*D) / M+D = EMPAVG (CROSS MULTIPLY M+D GOES TO RIGHT HAND SIDE)
= M-EMPAVG -5000M + D-EMPAVG+15000D = M-EMPAVG + D-EMPAVG (M-EMPAVG AND D-EMPAVG ON BOTH SIDES CANCEL OUT)
15000D = 5000M
M/D = 3/1 This is part to part ratio(manager to director ratio) which is telling us that for every 3 managers there is 1 director
Part to whole ratio for manager will be 3/4 i.e 3/4*100 = 75%
Not needed but just to show:
Part to whole ratio for directors will be 1/4 i.e 1/4*100 = 25%
D- NO OF DIRECTORS
E-NO OF EMPLOYEES
Let MAVG be managers avg salary
Let EMPAVG be employees average slaary
Let DIREAVG be directors avg salary
FORMAULA IS : (MAVG*M + DIRAVG*D) / M+D = EMPAVG (1)
To find ratio of M/D from which we can find the percent by multipying by 100
Stmt I
MAVG = EMPAVG-5000 (2)
cant find ratio m/n with this
INSUFF
Stmt II
DAVG = EMPAVG+15000 (3)
cant find ratio m/n with this
INSUFF
Stmt I and II together
Substitute in (1),
MAVG = EMPAVG-5000 FROM (2) AND DAVG = EMPAVG+15000 (3)
(MAVG*M + DIRAVG*D) / M+D = EMPAVG
= ((EMPAVG-5000)*M + (EMPAVG+15000)*D) / M+D = EMPAVG (CROSS MULTIPLY M+D GOES TO RIGHT HAND SIDE)
= M-EMPAVG -5000M + D-EMPAVG+15000D = M-EMPAVG + D-EMPAVG (M-EMPAVG AND D-EMPAVG ON BOTH SIDES CANCEL OUT)
15000D = 5000M
M/D = 3/1 This is part to part ratio(manager to director ratio) which is telling us that for every 3 managers there is 1 director
Part to whole ratio for manager will be 3/4 i.e 3/4*100 = 75%
Not needed but just to show:
Part to whole ratio for directors will be 1/4 i.e 1/4*100 = 25%
-
cramya
- Legendary Member
- Posts: 2467
- Joined: Thu Aug 28, 2008 6:14 pm
- Thanked: 331 times
- Followed by:11 members
Skyline,
In Jackcrystal's link u will see Sudhir's solution which is using weighted average but my approach above would be an algebric one(also using weighted average in my foruma (1)).
Either one is good and go with whichever(may be both also) u can understand better and will be able to apply in future problems.
I have tried to explain as best as I could but let me know if u still have questions.
Regards,
Cramya
In Jackcrystal's link u will see Sudhir's solution which is using weighted average but my approach above would be an algebric one(also using weighted average in my foruma (1)).
Either one is good and go with whichever(may be both also) u can understand better and will be able to apply in future problems.
I have tried to explain as best as I could but let me know if u still have questions.
Regards,
Cramya
Thanks Cramya. I have a clear picture now.cramya wrote:Skyline,
In Jackcrystal's link u will see Sudhir's solution which is using weighted average but my approach above would be an algebric one(also using weighted average in my foruma (1)).
Either one is good and go with whichever(may be both also) u can understand better and will be able to apply in future problems.
I have tried to explain as best as I could but let me know if u still have questions.
Regards,
Cramya
Regards,
skyline
