Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

It is currently 15 Jul 2019, 23:24

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

M07-03

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56235
M07-03  [#permalink]

Show Tags

New post 16 Sep 2014, 00:34
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

77% (02:45) correct 23% (03:32) wrong based on 75 sessions

HideShow timer Statistics


Two consultants, Mary and Jim, 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

_________________
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56235
Re M07-03  [#permalink]

Show Tags

New post 16 Sep 2014, 00:34
Official Solution:

Two consultants, Mary and Jim, 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 \(= \frac{1}{30}\) job/hour;

"Mary and Jim can type up a report in 12.5": \(\frac{1}{30} + \frac{1}{x}= \frac{1}{12.5}=\frac{2}{25}\), where \(x\) is the time needed for Jim to type the report alone. Solving gives \(x=\frac{150}{7}\);

"Jim needs 12 hours to edit the report": Jim's editing rate \(= \frac{1}{12}\) job/hour;

"Mary and Jim can edit a report in 7.5": \(\frac{1}{y}+\frac{1}{12}=\frac{1}{7.5}=\frac{2}{15}\), where \(y\) is the time needed for Mary to edit the report alone. Solving gives \(y=20\);

"How many hours will it take if Jim types the report and Mary edits it immediately after he is done": \(x+y= \frac{150}{7}+20 \approx 41.4\)


Answer: A
_________________
Manager
Manager
User avatar
Joined: 06 Mar 2014
Posts: 228
Location: India
GMAT Date: 04-30-2015
Reviews Badge
Re: M07-03  [#permalink]

Show Tags

New post 12 Oct 2014, 15:16
Most of the work/rate problems are causing trouble to me. Is there any thread dedicated to breaking down the common types and tricks, dealing with work/rate problems.

Something Similar to the distance speed time one: distance-speed-time-word-problems-made-easy-87481.html
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56235
Re: M07-03  [#permalink]

Show Tags

New post 12 Oct 2014, 15:18
1
earnit wrote:
Most of the work/rate problems are causing trouble to me. Is there any thread dedicated to breaking down the common types and tricks, dealing with work/rate problems.

Something Similar to the distance speed time one: distance-speed-time-word-problems-made-easy-87481.html


Theory on work/rate problems: work-word-problems-made-easy-87357.html

All DS work/rate problems to practice: search.php?search_id=tag&tag_id=46
All PS work/rate problems to practice: search.php?search_id=tag&tag_id=66
_________________
Manager
Manager
User avatar
Joined: 06 Mar 2014
Posts: 228
Location: India
GMAT Date: 04-30-2015
Reviews Badge
Re: M07-03  [#permalink]

Show Tags

New post 24 Feb 2015, 05:31
Bunuel wrote:
Official Solution:

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 \(= \frac{1}{30}\) job/hour;

"Mary and Jim can type up a report in 12.5": \(\frac{1}{30} + \frac{1}{x}= \frac{1}{12.5}=\frac{2}{25}\), where \(x\) is the time needed for Jim to type the report alone. Solving gives \(x=\frac{150}{7}\);

"Jim needs 12 hours to edit the report": Jim's editing rate \(= \frac{1}{12}\) job/hour;

"Mary and Jim can edit a report in 7.5": \(\frac{1}{y}+\frac{1}{12}=\frac{1}{7.5}=\frac{2}{15}\), where \(y\) is the time needed for Mary to edit the report alone. Solving gives \(y=20\);

"How many hours will it take if Jim types the report and Mary edits it immediately after he is done": \(x+y= \frac{150}{7}+20 \approx 41.4\)


Answer: A


My approach is the same except that in the end, i calculate the combined Rate for Mary and Jim after having found their new rates of editing and typing respectively.

So that in the end, the time taken would be the reciprocal of the Total Rate. But then with this approach my answer changes.

Please tell me what am i doing wrong here?
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56235
Re: M07-03  [#permalink]

Show Tags

New post 24 Feb 2015, 06:03
earnit wrote:
Bunuel wrote:
Official Solution:

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 \(= \frac{1}{30}\) job/hour;

"Mary and Jim can type up a report in 12.5": \(\frac{1}{30} + \frac{1}{x}= \frac{1}{12.5}=\frac{2}{25}\), where \(x\) is the time needed for Jim to type the report alone. Solving gives \(x=\frac{150}{7}\);

"Jim needs 12 hours to edit the report": Jim's editing rate \(= \frac{1}{12}\) job/hour;

"Mary and Jim can edit a report in 7.5": \(\frac{1}{y}+\frac{1}{12}=\frac{1}{7.5}=\frac{2}{15}\), where \(y\) is the time needed for Mary to edit the report alone. Solving gives \(y=20\);

"How many hours will it take if Jim types the report and Mary edits it immediately after he is done": \(x+y= \frac{150}{7}+20 \approx 41.4\)


Answer: A


My approach is the same except that in the end, i calculate the combined Rate for Mary and Jim after having found their new rates of editing and typing respectively.

So that in the end, the time taken would be the reciprocal of the Total Rate. But then with this approach my answer changes.

Please tell me what am i doing wrong here?


The point is that typing and editing are two separate actions: Jim types the report and Mary edits it immediately after he is done. Hence you cannot use combined rate for those two actions.

Hope it's clear.
_________________
Current Student
avatar
S
Joined: 18 Aug 2014
Posts: 324
GMAT ToolKit User Reviews Badge
Re: M07-03  [#permalink]

Show Tags

New post 03 May 2016, 13:14
Bunuel wrote:

"Jim needs 12 hours to edit the report": Jim's editing rate \(= \frac{1}{12}\) job/hour;

"Mary and Jim can edit a report in 7.5": \(\frac{1}{y}+\frac{1}{12}=\frac{1}{7.5}=\frac{2}{15}\), where \(y\) is the time needed for Mary to edit the report alone. Solving gives \(y=20\);


Can someone please break this out by step? I got here (as well the other step before this that is the same style of equation) during the problem but I got stuck proceeding on the math. Am I supposed to find the LCM for 7.5 and 12, add them then cross multiply? Do I just have to multiply 12 by 7.5 to quickly come up with a workable denominator?
_________________
Please help me find my lost Kudo's bird
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56235
Re: M07-03  [#permalink]

Show Tags

New post 04 May 2016, 06:54
redfield wrote:
Bunuel wrote:

"Jim needs 12 hours to edit the report": Jim's editing rate \(= \frac{1}{12}\) job/hour;

"Mary and Jim can edit a report in 7.5": \(\frac{1}{y}+\frac{1}{12}=\frac{1}{7.5}=\frac{2}{15}\), where \(y\) is the time needed for Mary to edit the report alone. Solving gives \(y=20\);


Can someone please break this out by step? I got here (as well the other step before this that is the same style of equation) during the problem but I got stuck proceeding on the math. Am I supposed to find the LCM for 7.5 and 12, add them then cross multiply? Do I just have to multiply 12 by 7.5 to quickly come up with a workable denominator?


\(\frac{1}{y}+\frac{1}{12}=\frac{1}{7.5}=\frac{2}{15}\)

\(\frac{1}{y}=\frac{2}{15}-\frac{1}{12}=\frac{8}{60}-\frac{5}{60}=\frac{3}{60}=\frac{1}{20}\)
_________________
Intern
Intern
User avatar
B
Joined: 06 Feb 2016
Posts: 47
Location: Poland
Concentration: Finance, Accounting
GMAT 1: 730 Q49 V41
GPA: 3.5
Re: M07-03  [#permalink]

Show Tags

New post 23 Sep 2017, 08:28
I think the part "immediately after he is done" is the key to answer this question. It means they are not working simultaneously.
Manager
Manager
User avatar
B
Joined: 31 Oct 2016
Posts: 106
Re: M07-03  [#permalink]

Show Tags

New post 26 Oct 2017, 11:36
How did I solve? Estimation approach.
Advantage: fast and accurate enough
Disadvantage: there is more logic than math and it won't give you the exact number. Only range

But I think that, if you are not math-genius and you can't solve that kind of problems for 2 minutes, you can try this approach.

Typing a report:
Mary and Jim together: 12.5 hours.
Only Mary: 30 hours
Mary and Mary together: 30/2 = 15 hours. So, it means that Jim is typing faster.
Jim and Jim together: less than 12.5 hours. About 12.5-(15-12.5) = 10 hours (since it is just approximation we can consider 10-11 hours).
It means that Jim working alone can type a report for about 20-22 hours.

Editing a report:
Mary and Jim together: 7.5 hours
Only Jim: 12 hours
Jim and Jim together: 12/2 = 6 hours. So, it means that Jim is editing also faster (good Jim)
Mary and Mary together: more than 7.5 hours. About (7.5-6)+7.5 = 9 hours (since it is just approximation we can consider 9-10 hours)
It means that Mary working alone can edit a report for about 18-20 hours.

Let's sum up. Our range is about (20+18) - (22+20) hours. Or about 38-42 hours ("-" do not read as "minus" here. It is a range).

Only A falls into this range.

Again - the official solution is much better and accurate. Use the official solution approach whenever is possible, but if you want to little bit save your time taking some risk, you can use approximation approach.
Manager
Manager
avatar
B
Joined: 26 Feb 2018
Posts: 76
Location: United Arab Emirates
GMAT 1: 710 Q47 V41
GMAT 2: 770 Q49 V47
Reviews Badge
Re: M07-03  [#permalink]

Show Tags

New post 10 Mar 2018, 13:25
This question is not mathematically difficult but it is time consuming.

The best approach is to guess. You know that working together they would to the typing and the editing in 20hrs. That means C, D and E can immediately be eliminated. B is still on the low side, too - why? We know that Mary takes 30 hrs alone to type and Mary + Jim take 12.5hrs. If Jim was the same speed as Mary, they would take 15hrs together - 12.5hrs isn't that much lower so we know that Jim isn't that much faster than Mary. So estimate a number in the mid 20s for Jim alone (say 25) Similarly, if Jim takes 12hrs to edit alone, Mary and Jim at the same rate would take 6hrs. 7.5 isn't that far away, so we know Mary is slower at editing but not by much. Estimate a number in the mid teens for Mary alone (say 16) and add - around 40.

A good example where quick educated guessing can save you a lot of time to use on questions
Intern
Intern
avatar
B
Joined: 15 Jan 2018
Posts: 13
GMAT 1: 570 Q45 V23
Reviews Badge
Re: M07-03  [#permalink]

Show Tags

New post 06 Nov 2018, 23:05
1
I think this question should be modified as :

Presenting Mary and Jim as separate entity is confusing

Two consultants,Mary & Jim, 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?
Manager
Manager
avatar
S
Joined: 20 Jul 2018
Posts: 75
WE: Corporate Finance (Investment Banking)
Re: M07-03  [#permalink]

Show Tags

New post 12 Nov 2018, 10:42
1
kabirdash, +1.
I missed the question because I hadn't been told that MARY & JIM were the consultants.
Intern
Intern
User avatar
B
Joined: 31 Jan 2018
Posts: 42
Location: Germany
GMAT 1: 610 Q44 V30
GPA: 3
WE: Supply Chain Management (Manufacturing)
GMAT ToolKit User
Re: M07-03  [#permalink]

Show Tags

New post 08 Jan 2019, 14:06
1
kabirdash wrote:
I think this question should be modified as :

Presenting Mary and Jim as separate entity is confusing

Two consultants,Mary & Jim, 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?


definitely! Was really confused if Mary & Jim are the two mentioned consultants or not.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56235
Re: M07-03  [#permalink]

Show Tags

New post 08 Jan 2019, 21:15
mskx wrote:
kabirdash wrote:
I think this question should be modified as :

Presenting Mary and Jim as separate entity is confusing

Two consultants,Mary & Jim, 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?


definitely! Was really confused if Mary & Jim are the two mentioned consultants or not.


Edited as suggested. Thank you.
_________________
GMAT Club Bot
Re: M07-03   [#permalink] 08 Jan 2019, 21:15
Display posts from previous: Sort by

M07-03

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  

Moderators: chetan2u, Bunuel






Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne