It is currently 23 Feb 2018, 06:20

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If two trains are 120 miles apart and are traveling toward each other

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

Hide Tags

Intern
Intern
avatar
Joined: 28 Sep 2016
Posts: 1
If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 01 Oct 2016, 02:12
8
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

64% (01:35) correct 36% (01:21) wrong based on 171 sessions

HideShow timer Statistics

If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet?

(A) 10
(B) 30
(C) 40
(D) 50
(E) 70

[Reveal] Spoiler:
As the question ask how far apart they will be 1 hour before they meet, I first calculated when they meet : 120- (30+40)= 12/7 h
so one hour before they meet is 12/7 - 1 = 5/7 h.
when the time is 5/7 they are 5/7 *70= 50 miles far apart .
anyway, the Question bank says that the correct answer is E, 70.
Can anyone tell me why? I think 70 is how much they are far apart 1 hour after they leave, not 1 hour before they meet.
[Reveal] Spoiler: OA

Last edited by Bunuel on 01 Oct 2016, 02:20, edited 1 time in total.
Renamed the topic and edited the question.
Expert Post
5 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43895
Re: If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 01 Oct 2016, 02:23
5
This post received
KUDOS
Expert's post
mc563427 wrote:
If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet?

(A) 10
(B) 30
(C) 40
(D) 50
(E) 70

[Reveal] Spoiler:
As the question ask how far apart they will be 1 hour before they meet, I first calculated when they meet : 120- (30+40)= 12/7 h
so one hour before they meet is 12/7 - 1 = 5/7 h.
when the time is 5/7 they are 5/7 *70= 50 miles far apart .
anyway, the Question bank says that the correct answer is E, 70.
Can anyone tell me why? I think 70 is how much they are far apart 1 hour after they leave, not 1 hour before they meet.


The combined rate of the two trains is 30 + 40 = 70 miles per hour. Therefore 1 hour before they meet the must be 70 miles apart (in the final 1 hour they will cover 70 miles to meet).

Answer: E.

P.S. Please follow the rules when posting a question: rules-for-posting-please-read-this-before-posting-133935.html Thank you.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Expert Post
1 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43895
Re: If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 01 Oct 2016, 02:24
1
This post received
KUDOS
Expert's post
Bunuel wrote:
mc563427 wrote:
If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet?

(A) 10
(B) 30
(C) 40
(D) 50
(E) 70

[Reveal] Spoiler:
As the question ask how far apart they will be 1 hour before they meet, I first calculated when they meet : 120- (30+40)= 12/7 h
so one hour before they meet is 12/7 - 1 = 5/7 h.
when the time is 5/7 they are 5/7 *70= 50 miles far apart .
anyway, the Question bank says that the correct answer is E, 70.
Can anyone tell me why? I think 70 is how much they are far apart 1 hour after they leave, not 1 hour before they meet.


The combined rate of the two trains is 30 + 40 = 70 miles per hour. Therefore 1 hour before they meet the must be 70 miles apart (in the final 1 hour they will cover 70 miles to meet).

Answer: E.

P.S. Please follow the rules when posting a question: rules-for-posting-please-read-this-before-posting-133935.html Thank you.


Similar question to practice: 12-easy-pieces-or-not-126366.html#p1033924

Hope it helps.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Intern
Intern
avatar
Joined: 07 Mar 2013
Posts: 6
Re: If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 17 Oct 2016, 05:30
this is a little lengthier way of doing but mistake proof method.
They would meet in 120/70 = 12/7 hours
1 hour earlier 5/7 hours
distance between trains = total distance -(distance covered by train A + distance covered by train B)

= 120-(5/7(40+30)) [ distance of A = 5/7* 40; like wise distance by B]
= 70 Km

Kudos! if u like this
SVP
SVP
avatar
P
Joined: 12 Dec 2016
Posts: 1908
Location: United States
GMAT 1: 700 Q49 V33
GPA: 3.64
GMAT ToolKit User Premium Member
Re: If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 03 Apr 2017, 18:31
It is still hard for me to focus on the right detail. It is because in this case, I may miss one or two important details in quantitative problems.
Expert Post
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2016
Re: If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 06 Apr 2017, 08:43
mc563427 wrote:
If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet?

(A) 10
(B) 30
(C) 40
(D) 50
(E) 70


Since we have a converging rate problem, we can use the following formula:

distance 1 train + distance 2 train = total distance

We can let t be the time the two trains will meet. Thus:

30t + 40t = 120

70t = 120

t = 120/70 = 12/7 hours

Since we want to find the distance apart 1 hour before they meet, the distance traveled by one train is 30(12/7 - 1) = 30(5/7) = 150/7 miles and the distance traveled by the other train is 40(12/7 - 1) = 40(5/7) = 200/7 miles. Thus, the total distance traveled by the two trains is 150/7 + 200/7 = 350/7 = 50 miles. Therefore, they are 120 - 50 = 70 miles apart 1 hour before they meet.

Alternative solution:

A much shorter approach to solve this problem is to argue the following:

Since in 1 hour, train 1 travels 30 miles and train 2 travels 40 miles, 1 hour before they meet, they should be 30 + 40 = 70 miles apart.

Answer: E
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Manager
Manager
avatar
S
Status: active
Joined: 25 Jan 2016
Posts: 173
Location: India
Concentration: Finance, Entrepreneurship
GPA: 4
WE: Web Development (Computer Software)
Re: If two trains are 120 miles apart and are traveling toward each other [#permalink]

Show Tags

New post 08 Apr 2017, 06:00
If two trains are 120 miles apart and are traveling toward each other at constant rate of 30 miles per hour and 40 miles per hour, respectively, how far apart will they be 1 hour before they meet?

(A) 10
(B) 30
(C) 40
(D) 50
(E) 70

relative speed is 30+40=70 miles per hour

answer is E
Re: If two trains are 120 miles apart and are traveling toward each other   [#permalink] 08 Apr 2017, 06:00
Display posts from previous: Sort by

If two trains are 120 miles apart and are traveling toward each other

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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

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®.