GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Oct 2019, 02:49 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  Three medical experts, working together at the same constant rate, can

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

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58410
Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

1
12 00:00

Difficulty:   35% (medium)

Question Stats: 68% (01:21) correct 32% (01:56) wrong based on 378 sessions

HideShow timer Statistics

Tough and Tricky questions: Work Problems.

Three medical experts, working together at the same constant rate, can write an anatomy textbook in 24 days. How many additional experts, working together at this same constant rate, are needed to write the textbook in 9 days?

A. 2
B. 3
C. 5
D. 8
E. 15

Kudos for a correct solution.

_________________
SVP  Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1747
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

5
Answer = C = 5

Combined rate = $$\frac{1}{24}$$

Individual rate = $$\frac{1}{72}$$

Required (combined rate) = $$\frac{1}{9}$$

Let say "x" experts additionally required; 3 experts are already present

$$\frac{3+x}{72} =\frac{1}{9}$$

x = 5
_________________
Kindly press "+1 Kudos" to appreciate General Discussion
Intern  Joined: 29 Sep 2014
Posts: 15
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

2
"Three medical experts, working together at the same constant rate, can write an anatomy textbook in 24 days."
This means that the rate of each individual doctor is 1/(3*24).

If n is the number of doctors needed to complete the work in 9 days, we have n/(3*24)*9=1.
Therefore, n=8.

8-3=5 additional doctors are needed.

Intern  Joined: 06 Dec 2012
Posts: 23
Concentration: Finance, International Business
GMAT 1: 510 Q46 V21 GPA: 3.5
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

1
1
Since 3 people take 24 days to complete a work,

Rate * No.Of people= Work/time
Rate of 3 people= 1/24 per day.

so rate of single person is =1/(24*3)=1/72 work per day.

So to complete 1 work in Time=9 days,
Let n= no.of work-force / people needed.

1/72 * N= 1/9..............since rate of 1 person is 1/72. & Time is 9 days.
so N=8 people needed to complete 1 work in 9 days.

So additional people needed are= 8-3=5 people needed as 3 people are already working.

So Ans is 5 people needed.
Manager  Joined: 10 Sep 2014
Posts: 96
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

1
Answer choices A and B make no sense so we are quickly down to C, D, E.

Since each worker works at the same rate, I tried to figure out what fraction each worker was doing each day. Each worker must have been writing 1/72 of the textbook each day for the 24 days. So now we need to figure out how many it takes to write it in 9 days.

5 additional writers means that each day 8 writers are collectively writing 8/72 (1/9th) of the textbook.

Math Expert V
Joined: 02 Sep 2009
Posts: 58410
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

1
Bunuel wrote:

Tough and Tricky questions: Work Problems.

Three medical experts, working together at the same constant rate, can write an anatomy textbook in 24 days. How many additional experts, working together at this same constant rate, are needed to write the textbook in 9 days?

A. 2
B. 3
C. 5
D. 8
E. 15

Kudos for a correct solution.

Official Solution:

Three medical experts, working together at the same constant rate, can write an anatomy textbook in 24 days. How many additional experts, working together at this same constant rate, are needed to write the textbook in 9 days?

A. 2
B. 3
C. 5
D. 8
E. 15

We are asked to determine how many additional experts must be added to our team of 3 in order to decrease the time required to write an anatomy textbook from 24 days to 9 days.

We can plug in the values we are given into the work formula, $$w = rt$$, where $$w$$ is the amount of work done, $$r$$ is the rate at which the work is performed, and $$t$$ is the time it takes the work to be completed. In this case, $$w = 1$$ (since there is one textbook), $$t = 24$$, and $$r$$ is unknown. Thus, the original situation can be represented by the formula: $$1 = (3r)(24) = 72r$$. Note that we use $$3r$$ because there are 3 people working, each at the same rate of $$r$$.

We solve for $$r$$ by dividing both sides by 72, leaving $$r = \frac{1}{72}$$ book per day. This is the rate at which each expert works.

We use this value of $$r$$ to solve for $$k$$, the number of experts it would take to write a book in 9 days. In this new equation, $$w$$ will still equal 1, $$r = \frac{1}{72}k$$, and $$t = 9$$. This gives us: $$1 = (\frac{1}{72}k)(9) = \frac{1}{8}k$$. We solve for $$k$$ by multiplying both sides by $$8$$. We find that $$k = 8$$. So it will take 8 experts to finish the book in 9 days.

Remember, though, that we are looking for the number of additional experts. Since we already have 3 experts, in order to get 8, we need an additional $$8 - 3 = 5$$ experts.

_________________
Intern  Joined: 08 Dec 2014
Posts: 7
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

this is a case of simple unitary method.
Since all the experts have the same rate of work we don't need to calculate the rate. The values provided may be written as :
Let the work ie to write the books be 1.
No of Med Exp Amount of Work Days to finish the work
3 1 24
x 1 9
x = (3 * 1 * 24)/ 9 = 8

Therefore additional needed : 8 - 3 = 5
ans: c
Manager  B
Joined: 17 Jul 2016
Posts: 54
Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

1
1
What is the most efficient way to solve this problem? Remember, the gmat doesn't reward you for being very theoretical and

complicated in your reasoning. Your job is to solve it as efficiently as possible.

$$3(24)=9(x)$$

Dividing both sides by 3 we obtain $$24=3x$$

Hence, $$x=8$$.

we went from 3 doctors to 8 doctors, so 5 more were needed.

We can save a step and set up this equation.

$$3(24)=(3+x)(9)$$

Dividing both sides by 3(3) we obtain $$8=3+x$$

Hence, $$x =5$$
Senior PS Moderator V
Joined: 26 Feb 2016
Posts: 3334
Location: India
GPA: 3.12
Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

Since 3 medical experts working at a constant rate write a textbook in 24 days.

Lets assume that the book has 72(3*24) pages
Now, each of these experts must write 1 page a day

Since x additional experts are added to write the same book in 9 days,
$$\frac{72}{9} = 8$$ pages need to be written in a day.
We know that the existing 3 experts write 3 of those pages, leaving 5 pages to be written everyday.

So, we will need 5 additional experts to write the book(Option C)
_________________
You've got what it takes, but it will take everything you've got
SVP  V
Status: It's near - I can see.
Joined: 13 Apr 2013
Posts: 1686
Location: India
Concentration: International Business, Operations
Schools: INSEAD Jan '19
GPA: 3.01
WE: Engineering (Real Estate)
Re: Three medical experts, working together at the same constant rate, can  [#permalink]

Show Tags

Bunuel wrote:

Tough and Tricky questions: Work Problems.

Three medical experts, working together at the same constant rate, can write an anatomy textbook in 24 days. How many additional experts, working together at this same constant rate, are needed to write the textbook in 9 days?

A. 2
B. 3
C. 5
D. 8
E. 15

Kudos for a correct solution.

Men * Rate * Time = Work

3 * Rate * 24 = 1

Rate of 1 Men = 1/72

Now , Work = 1 book

Time = 9 hours

Rate = 1/72

Men * Rate * Time = Work

Men * 1/72 * 9 = 1

Men = 8

Therefore extra men needed = 8 - 3 = 5

_________________
"Do not watch clock; Do what it does. KEEP GOING." Re: Three medical experts, working together at the same constant rate, can   [#permalink] 27 Feb 2019, 23:38
Display posts from previous: Sort by

Three medical experts, working together at the same constant rate, can

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

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