|
Author |
Message |
|
TAGS:
|
|
|
SVP
Joined: 01 Sep 2010
Posts: 1797
Followers: 64
Kudos [?]:
650
[0], given: 478
|
On his trip to Alaska, Joe traveled y percent of the total [#permalink]
 31 Oct 2012, 11:46
Question Stats:
71% (02:54) correct
28% (04:38) wrong based on 35 sessions
On his trip to Alaska, Joe traveled y percent of the total distance at an average speed of 50 miles per hour and the rest of the distance at an average speed of 70 miles per hour. What was Joe’s average speed in miles per hour for the whole trip in terms of y? (A) 70(50 – y) (B) (y + 60)/4 (C) 10,000 – 199y (D) 17,500/(y + 250) (E) y/2 + 35 If the first part is at 50 mile/h and the second part is 70 miles/h the overall speed is the toral distance / total time. Pick a number for distance we can use 350. so the time for first part is 7 and for the rest is 5. in the end we will have 26. something, but testing answer choices nothing comes up  ( where I'm wrong PS: I could use a bit of logic and come to the answer easier, but .............
_________________
KUDOS is the good manner to help the entire community.
|
|
|
|
|
|
|
Manager
Joined: 27 Feb 2012
Posts: 136
Followers: 1
Kudos [?]:
22
[2] , given: 20
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
31 Oct 2012, 12:41
2
This post received
KUDOS
As you need a quick logical answer let me try Lety distance be X so Time 1 = XY/100*50 Time 2 = X(100-Y)/100*70 Avg Speed = Total Distance / Total Time = X/ Time 1 + Time 2 Ans D reason is simple...X cancels and Y reamins in denominator only 1 option has the same
_________________
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Please +1 KUDO if my post helps. Thank you.
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 12101
Followers: 1879
Kudos [?]:
10111
[2] , given: 960
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
01 Nov 2012, 06:27
2
This post received
KUDOS
carcass wrote: On his trip to Alaska, Joe traveled y percent of the total distance at an average speed of 50 miles per hour and the rest of the distance at an average speed of 70 miles per hour. What was Joe’s average speed in miles per hour for the whole trip in terms of y? (A) 70(50 – y) (B) (y + 60)/4 (C) 10,000 – 199y (D) 17,500/(y + 250) (E) y/2 + 35 If the first part is at 50 mile/h and the second part is 70 miles/h the overall speed is the toral distance / total time. Pick a number for distance we can use 350. so the time for first part is 7 and for the rest is 5. in the end we will have 26. something, but testing answer choices nothing comes up ( where I'm wrong PS: I could use a bit of logic and come to the answer easier, but ............. Say y=100%, so say Joe traveled entire trip at an average speed of 50 miles per hour. So, in this case we'd have that his average speed is simply 50 miles per hour. Now, plug y=100 into the answer choices and see which one yields 50. Only answer choice D fits. Or: say y=0%. In this case we'd have that Joe's average speed is 70 miles per hour. Now, plug y=0 into the answer choices and see which one yields 70. Again, only answer choice D fits. Answer: D. Hope it helps.
_________________
PLEASE READ AND FOLLOW: 11 Rules for Posting!!!
RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders
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. NEW!!! ,11 Mixed Questions NEW!!!, 12 Fresh Meat NEW!!!
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. NEW!!!, 11 New DS set. NEW!!!
What are GMAT Club Tests?
25 extra-hard Quant Tests
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Intern
Joined: 27 Aug 2012
Posts: 14
Followers: 0
Kudos [?]:
1
[0], given: 8
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
06 Nov 2012, 09:01
BangOn wrote: As you need a quick logical answer let me try
Lety distance be X
so Time 1 = XY/100*50
Time 2 = X(100-Y)/100*70
Avg Speed = Total Distance / Total Time
= X/ Time 1 + Time 2
Ans D
reason is simple...X cancels and Y reamins in denominator
only 1 option has the same I deducted the above within 30 secs but took another 3 mins to solve the whole mess to get to the ans choice. As you rightly said if we notice Y remains in deno for only one choice, life becomes easier. I tend to go the conventional way every time not the GMAT way Any other tricks like this which could help save TIME?
|
|
|
|
|
|
Intern
Joined: 27 Aug 2012
Posts: 14
Followers: 0
Kudos [?]:
1
[0], given: 8
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
06 Nov 2012, 09:10
Another way - less than 2 mins
Take Total distance = 100
1) y% of 100 at 50 mi/hr = distance is y miles -- So its y miles at 50 mi/hr
2) remaining (100-y) miles at 70 mi/hr
Avg spd = Total Dist/Total Time = 100/(y/50 + (100-y)/70) -> leads to D.(in case there are more choices with y in deno)
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 12101
Followers: 1879
Kudos [?]:
10111
[0], given: 960
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
06 Nov 2012, 09:38
|
|
|
|
|
|
Senior Manager
Status: Prevent and prepare. Not repent and repair!!
Joined: 13 Feb 2010
Posts: 268
Location: India
Concentration: Technology, General Management
GPA: 3.75
WE: Sales (Telecommunications)
Followers: 8
Kudos [?]:
11
[0], given: 256
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
15 Nov 2012, 10:50
i just plugged in some random nos- say Total distance=100 y=30% Then ball parked to find that D is the ans.
_________________
I've failed over and over and over again in my life and that is why I succeed--Michael Jordan
Kudos drives a person to better himself every single time. So Pls give it generously
Wont give up till i hit a 700+
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 12101
Followers: 1879
Kudos [?]:
10111
[1] , given: 960
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
16 Nov 2012, 03:22
1
This post received
KUDOS
|
|
|
|
|
|
Intern
Joined: 26 Jul 2012
Posts: 6
Followers: 0
Kudos [?]:
0
[0], given: 0
|
Re: On his trip to Alaska, Joe traveled y percent of the total [#permalink]
17 Nov 2012, 16:59
rajathpanta wrote: i just plugged in some random nos-
say Total distance=100
y=30%
Then ball parked to find that D is the ans. No need to assume the value of y. Assume total distance = 100. Therefore total time taken = (y/50) + (100-y)/70 = (y + 250)/175 Average speed = 100/( (y + 250)/175) = 175000/ (y + 250)
|
|
|
|
|
|
|
Re: On his trip to Alaska, Joe traveled y percent of the total
[#permalink]
17 Nov 2012, 16:59
|
|
|
|
|
|
|
|
|
|
|
close
