Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 31 Aug 2016, 00:14

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# RT=W Report (m07q03)

Author Message
CEO
Joined: 21 Jan 2007
Posts: 2756
Location: New York City
Followers: 9

Kudos [?]: 746 [2] , given: 4

### Show Tags

14 Nov 2007, 11:16
2
KUDOS
1
This post was
BOOKMARKED
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

(A) 41.4
(B) 34.1
(C) 13.4
(D) 12.4
(E) 10.8

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions
Manager
Joined: 25 Jul 2007
Posts: 108
Followers: 1

Kudos [?]: 18 [5] , given: 0

### Show Tags

14 Nov 2007, 11:28
5
KUDOS
Let time taken by 'j' to type be 'j'.

We know that 1/m + 1/j = 1/12.5

i.e. 1/30 + 1/j = 1/12.5

i.e. (30+j)/30j = 1/12.5

i.e. 375 = 30j-12.5j=17.5j

i.e. j = 375/17.5=150/7

Let time taken by 'm' to edit be 'x' and that by 'j' be 'y'.

We know that 1/x + 1/y = 1/7.5

i.e. 1/x + 1/12 = 1/7.5

i.e. (12+x)/12x = 1/7.5

i.e. 90 = 12x-7.5x=4.5x

i.e. x = 90/4.5 = 20

Therefore answer = 150/7+20 = 41.4
Manager
Joined: 29 Nov 2009
Posts: 107
Location: United States
Followers: 1

Kudos [?]: 30 [0], given: 5

### Show Tags

09 Dec 2009, 07:16
Right, and once you solve for either 150/7 or 20, you can immediately eliminate all possibilities other than A and B. This would give you a 50% guess for half the work if you're low on time.
Intern
Joined: 23 Nov 2009
Posts: 1
Followers: 0

Kudos [?]: 0 [0], given: 1

### Show Tags

09 Dec 2009, 12:24
Hi
I think the question should be re-written as a "which is the closest" or "approximately how long" question since 150/7 doesn't exactly equal 21.4... It's close to it: 21.42857...
There would never be an approximate right answer on the GMAT on a question which asks for a specific quantity
Manager
Joined: 23 Oct 2010
Posts: 87
Location: India
Followers: 3

Kudos [?]: 26 [0], given: 6

### Show Tags

16 Dec 2010, 06:02
A.

This is calculation intensive. What would be a shorter solution?
I solved like this:
1/30 + 1/x = 1/12.5 => x = 21.4
1/12+1/y = 1/7.5 => y = 20

Total = 21.4 + 20 = 41.4
Manager
Joined: 23 Oct 2010
Posts: 87
Location: India
Followers: 3

Kudos [?]: 26 [4] , given: 6

### Show Tags

16 Dec 2010, 06:11
4
KUDOS
bmwhype2 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

* 41.4
* 34.1
* 13.4
* 12.4
* 10.8

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

Well, this is how I figured a shorter solution:

M takes 30 hrs, two cons of equal cap take 12.5 *2 = 25 hrs each. Hence J will take less than 25 hrs (how much less --> guess above 20 at least?)
J takes 12 hrs, two cons of equal cap take 7.5 * 2 = 15 hrs each. Hence M will take more than 15 hrs (how much greater --> guess around 18)
Add them = GT20 + GT 15 = 35 . Only one option is above 35
SVP
Joined: 16 Jul 2009
Posts: 1629
Schools: CBS
WE 1: 4 years (Consulting)
Followers: 40

Kudos [?]: 891 [0], given: 2

### Show Tags

16 Dec 2010, 12:28
sleekmover wrote:
bmwhype2 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

* 41.4
* 34.1
* 13.4
* 12.4
* 10.8

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

Well, this is how I figured a shorter solution:

M takes 30 hrs, two cons of equal cap take 12.5 *2 = 25 hrs each. Hence J will take less than 25 hrs (how much less --> guess above 20 at least?)
J takes 12 hrs, two cons of equal cap take 7.5 * 2 = 15 hrs each. Hence M will take more than 15 hrs (how much greater --> guess around 18)
Add them = GT20 + GT 15 = 35 . Only one option is above 35

why you dont guess 18 (< than 25) for J and 16,1 (> than 15) for M, and therefore you get 18+16,1=34,1 and get B??
_________________

The sky is the limit
800 is the limit

GMAT Club Premium Membership - big benefits and savings

Manager
Joined: 23 Oct 2010
Posts: 87
Location: India
Followers: 3

Kudos [?]: 26 [0], given: 6

### Show Tags

16 Dec 2010, 13:20
noboru wrote:
sleekmover wrote:
bmwhype2 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

* 41.4
* 34.1
* 13.4
* 12.4
* 10.8

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

Well, this is how I figured a shorter solution:

M takes 30 hrs, two cons of equal cap take 12.5 *2 = 25 hrs each. Hence J will take less than 25 hrs (how much less --> guess above 20 at least?)
J takes 12 hrs, two cons of equal cap take 7.5 * 2 = 15 hrs each. Hence M will take more than 15 hrs (how much greater --> guess around 18)
Add them = GT20 + GT 15 = 35 . Only one option is above 35

why you dont guess 18 (< than 25) for J and 16,1 (> than 15) for M, and therefore you get 18+16,1=34,1 and get B??

Vaild question noburo: Here is the explanation->
J = 12, with same cap cons 1 = 15 and cons 2 = 15, Hence M needs to compensate for less hrs of J. at least 3 needs to be added to common hrs (assuming we are looking at Arithmetic mean)
M = 30, with same cap Cons 1 = 25 and Cons 2 = 25, , Hence J needs to compensate for more hrs of M. At lease 5 needs to be subtracted from common hrs (assuming we are looking at Arithmetic Mean)

We should also understand a bit about harmonic and arithmentic, a concept illustrated here: http://en.wikipedia.org/wiki/Harmonic_mean
Some points from the above post to consider:
For all positive data sets containing at least one pair of nonequal values, the harmonic mean is always the least of the three means, while the arithmetic mean is always the greatest of the three and the geometric mean is always in between
Since the harmonic mean of a list of numbers tends strongly toward the least elements of the list

In certain situations, especially many situations involving rates and ratios, the harmonic mean provides the truest average. For instance, if a vehicle travels a certain distance at a speed x (e.g. 60 kilometres per hour) and then the same distance again at a speed y (e.g. 40 kilometres per hour), then its average speed is the harmonic mean of x and y (48 kilometres per hour), and its total travel time is the same as if it had traveled the whole distance at that average speed

Hope this explains
Intern
Joined: 08 Dec 2011
Posts: 1
Followers: 0

Kudos [?]: 1 [1] , given: 0

### Show Tags

20 Dec 2011, 21:36
1
KUDOS

Since there two consultants, one consultant can type in 12.5*2=25 hours, and edit in 7.5*2=15 hours. To type and edit for one consultant it will take 25+15=40 hours.

Mary can type in 30 hours, which is 20% slower than let's say average.
Jim can edit in 12 hours, which is 20% faster than average.

If Jim types, it will take for Jim 25*0.8%=20 hours.
If Mary edits, it will take for Mary 15*1.2%=18 hours.

Together 38 hours, which is closer to A. Therefore the correct answer is A.
Math Expert
Joined: 02 Sep 2009
Posts: 34514
Followers: 6308

Kudos [?]: 80026 [2] , given: 10024

### Show Tags

20 Dec 2012, 06:19
2
KUDOS
Expert's post
bmwhype2 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

(A) 41.4
(B) 34.1
(C) 13.4
(D) 12.4
(E) 10.8

[Reveal] Spoiler: OA
A

Source: GMAT Club Tests - hardest GMAT questions

Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, approximately how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

A. 41.4
B. 34.1
C. 13.4
D. 12.4
E. 10.8

Break down the problem into two pieces: typing and editing.

"Mary needs 30 hours to type the report" --> Mary's typing rate = 1/30 job/hour;
"Mary and Jim can type up a report in 12.5" and --> 1/30+1/x=1/12.5=2/25, where x is the time needed for Jim to type the report alone --> x=150/7;

"Jim needs 12 hours to edit the report" --> Jim's editing rate = 1/12 job/hour;
"Mary and Jim can edit a report in 7.5" and --> 1/y+1/12=1/7.5=2/15, where y is the time needed for Mary to edit the report alone --> y=20;

"How many hours will it take if Jim types the report and Mary edits it immediately after he is done" --> x+y=150/7+20=~41.4

_________________
Current Student
Joined: 04 Nov 2012
Posts: 90
Location: United States
GMAT 1: Q44 V38
GPA: 3.7
WE: Science (Pharmaceuticals and Biotech)
Followers: 1

Kudos [?]: 34 [0], given: 82

### Show Tags

20 Dec 2012, 08:57
I got the correct answer, but it took me >5 minutes! Did any of you solve it in 2 or less?
_________________

kudos are appreciated

Current Student
Joined: 04 Nov 2012
Posts: 90
Location: United States
GMAT 1: Q44 V38
GPA: 3.7
WE: Science (Pharmaceuticals and Biotech)
Followers: 1

Kudos [?]: 34 [0], given: 82

### Show Tags

20 Dec 2012, 09:01
Also, I don't believe this question is GMAT quality. It took me a few minutes to figure out what they were asking and that the two consultants were Mary and Jim since it wasn't stated. A correction is in order.
_________________

kudos are appreciated

Intern
Joined: 24 Nov 2012
Posts: 3
Followers: 0

Kudos [?]: 2 [0], given: 13

### Show Tags

20 Dec 2012, 16:28
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

(A) 41.4
(B) 34.1
(C) 13.4
(D) 12.4
(E) 10.8
Magoosh GMAT Instructor
Joined: 28 Dec 2011
Posts: 3319
Followers: 1129

Kudos [?]: 4966 [1] , given: 54

### Show Tags

20 Dec 2012, 19:06
1
KUDOS
Expert's post
david1983 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?
(A) 41.4
(B) 34.1
(C) 13.4
(D) 12.4
(E) 10.8

This is a very hard question, in part because it is not phrased particularly well. In particular, I believe the question wants us to understand that the "two consultant" mentioned in the first sentence are not two consultants in general, but rather, quite specifically, Mary & Jim.

Let's consider the typing rates.
Mary's rate = 1/30 (papers per hour)
Jim's rate = 1/X ----- where X = the hours it would take Jim to type one paper
Combined rate = 1/12.5 = 2/25
Big Idea: We can always add rates.
(Mary's rate) + (Jim's rate) = (combined rate)
(1/30) + (1/X) = 2/25
1/X = 2/25 - 1/30 = 12/150 - 5/150 = 7/150

X = 150/7 = 21 3/7

Now, let's consider the editing rates:
Mary's rate = 1/Y ------ where Y = the hours it would take Mary to edit one paper
Jim's rate = 1/12
Combined rate = 1/7.5 = 2/15
(Mary's rate) + (Jim's rate) = (combined rate)
1/Y + 1/12 = 2/15
1/Y = 2/15 - 1/12 = 8/60 - 5/60 = 3/60 = 1/20
Y = 20

Combined time = X + Y = 21 3/7 + 20 = 41 3/7 = 41.42857

Here's a related blog you may find helpful:
http://magoosh.com/gmat/2012/gmat-work-rate-questions/

Does all this make sense?

Mike
_________________

Mike McGarry
Magoosh Test Prep

Senior Manager
Joined: 13 Aug 2012
Posts: 464
Concentration: Marketing, Finance
GMAT 1: Q V0
GPA: 3.23
Followers: 25

Kudos [?]: 386 [2] , given: 11

### Show Tags

20 Dec 2012, 21:16
2
KUDOS
david1983 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

(A) 41.4
(B) 34.1
(C) 13.4
(D) 12.4
(E) 10.8

Given:
$$\frac{1}{M_{edit}}+\frac{1}{J_{edit}}=\frac{1}{7.5}=\frac{2}{15}$$
$$\frac{1}{M_{type}}+\frac{1}{J_{type}}=\frac{1}{12.5}=\frac{2}{25}$$
$$\frac{1}{M_{type}}=\frac{1}{30}$$
$$\frac{1}{J_{edit}}=\frac{1}{12}$$

Solve for $$M_{edit} + J_{edit}$$:

$$\frac{1}{M_{edit}}+\frac{1}{J_{edit}} - \frac{1}{J_{edit}}=\frac{2}{15}-\frac{1}{12}=\frac{1}{20}$$

$$\frac{1}{M_{type}}+\frac{1}{J_{type}}-\frac{1}{M_{type}}=\frac{2}{25}-\frac{1}{30}=\frac{7}{150}$$

$$M_{edit} + J_{type} = 20 + 21.4=41.4$$
_________________

Impossible is nothing to God.

Current Student
Status: Final Lap Up!!!
Affiliations: NYK Line
Joined: 21 Sep 2012
Posts: 1095
Location: India
GMAT 1: 410 Q35 V11
GMAT 2: 530 Q44 V20
GMAT 3: 630 Q45 V31
GPA: 3.84
WE: Engineering (Transportation)
Followers: 38

Kudos [?]: 476 [0], given: 70

### Show Tags

20 Dec 2012, 22:11
The question was not really difficult.....But lot of calculation involved...Can anyone suggest a shorter method
Math Expert
Joined: 02 Sep 2009
Posts: 34514
Followers: 6308

Kudos [?]: 80026 [0], given: 10024

### Show Tags

21 Dec 2012, 03:06
david1983 wrote:
Two consultants can type up a report in 12.5 hours and edit it in 7.5 hours. If Mary needs 30 hours to type the report and Jim needs 12 hours to edit it alone, how many hours will it take if Jim types the report and Mary edits it immediately after he is done?

(A) 41.4
(B) 34.1
(C) 13.4
(D) 12.4
(E) 10.8

Merging similar topics. Please refer to the solutions above.
_________________
Intern
Joined: 01 Apr 2013
Posts: 19
Followers: 0

Kudos [?]: 3 [0], given: 72

### Show Tags

16 Dec 2013, 12:35
Yes, this question isn't hard, it's just phrased poorly. The most difficult part is understanding that Jim and Mary themselves are indeed the two consultants.
Manager
Joined: 04 Oct 2013
Posts: 162
Location: India
GMAT Date: 05-23-2015
GPA: 3.45
Followers: 3

Kudos [?]: 96 [0], given: 54

### Show Tags

24 Dec 2013, 02:50
Archit143 wrote:
The question was not really difficult.....But lot of calculation involved...Can anyone suggest a shorter method

Let us assume typing to be a work of 750 units (a common multiple of 25/2 and 30).
So, in one day both Jim and Mary type 60 units (750/12.5) and Mary alone types 25 units (750/30).
Thus, Jim types 35 units (60-35) per day or takes approximately 21.4 days (=750/35)......(1)

Let us assume editing to be a work of 60 units (a common multiple of 15/2 and 12).
So, in one day both Jim and Mary edit 8 units (60/7.5) and Jim alone edits 5 units (60/12).
Thus, Mary edits 3 units (8 - 5) per day or takes 20 days (=60/3)................................ (2)

Combining (1) and (2), we get 21.4 + 20 or 41.4 days.
Re: RT=W Report (m07q03)   [#permalink] 24 Dec 2013, 02:50
Display posts from previous: Sort by

# RT=W Report (m07q03)

Moderator: Bunuel

 Powered by phpBB © phpBB Group and phpBB SEO Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.