Forum Home > GMAT > Quantitative > Problem Solving (PS)
Events & Promotions
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Oct 1009:00 AM PDT
-12:00 PM PDT
Are you ready to take the next step in your academic and professional journey? If you’re aspiring to join one of the top 15 MBA programs, we’ve got an exciting opportunity just for you! Welcome to the GMAT Club's Free Interview Prep Event
Oct 1010:00 AM EDT
-11:00 AM EDT
Have you ever wondered how to score a PERFECT 805 on the GMAT? Meet Julia, a banking professional who used the Target Test Prep course to achieve this incredible feat. Julia's story is nothing short of an inspiration.
Oct 0810:00 AM EDT
-11:59 PM EDT
For a limited time use code TAKE15 to save on prep. Valid on Complete Course, Advanced Course, Bootcamp Course, Tutoring, and the Executive Assessment Course. This discount ends October 28, 2024.
Oct 1110:00 AM EDT
-11:00 AM EDT
Think a 100% GMAT Verbal score is out of your reach? Target Test Prep will make you think again! Our course uses techniques such as topical study and spaced repetition to maximize knowledge retention and make studying simple and fun.
Oct 1211:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment- Oct 13
11:00 AM IST
-01:00 PM IST
Attend this session to evaluate your current skill level, learn process skills, and solve through tough Arithmetic questions
Khalil drove 120 kilometers in a certain amount of time. What was his
[#permalink]
21 Sep 2019, 16:02
21 Sep 2019, 16:02
4
Kudos
123
Bookmarks
Show timer
00:00
A
B
C
D
E
Difficulty:
95%
(hard)
Question Stats:
50% (02:24) correct
50%
(02:16)
wrong
based on 1884
sessions
Khalil drove 120 kilometers in a certain amount of time. What was his average speed, in kilometers per hour, during this time?
(1) If Khalil had driven at an average speed that was 5 kilometers per hour faster, his driving time would have been reduced by 20 minutes.
(2) If Khalil had driven at an average speed that was 25% faster, his driving time would have been reduced by 20%.
DS01951.01
(1) If Khalil had driven at an average speed that was 5 kilometers per hour faster, his driving time would have been reduced by 20 minutes.
(2) If Khalil had driven at an average speed that was 25% faster, his driving time would have been reduced by 20%.
DS01951.01
Re: Khalil drove 120 kilometers in a certain amount of time. What was his
[#permalink]
29 Sep 2019, 19:42
29 Sep 2019, 19:42
14
Kudos
7
Bookmarks
gmatt1476
Khalil drove 120 kilometers in a certain amount of time. What was his average speed, in kilometers per hour, during this time?
(1) If Khalil had driven at an average speed that was 5 kilometers per hour faster, his driving time would have been reduced by 20 minutes.
(2) If Khalil had driven at an average speed that was 25% faster, his driving time would have been reduced by 20%.
DS01951.01
(1) If Khalil had driven at an average speed that was 5 kilometers per hour faster, his driving time would have been reduced by 20 minutes.
(2) If Khalil had driven at an average speed that was 25% faster, his driving time would have been reduced by 20%.
DS01951.01
We know that the distance is 120. Let r be his average speed. The original question: r=?
1) At the old speed, his driving time is 120/r. At the new speed, his driving time would be 120/(r+5). We can set up an equation about his new driving time, which is 1/3 hour less than his old driving time.
\(\frac{120}{r+5}=\frac{120}{r}-\frac{1}{3}\)
\(360r=360r+1800-r^2-5r\)
\(r^2+5r-1800=0\)
Since c/a is negative for the quadratic equation above, its two roots have different signs. However, only its positive root applies to the context of the problem.
Thus, we could get a unique value to answer the original question. \(\implies\) Sufficient
2) At his new speed, his driving time would be 120/(1.25r). We can set up an equation about his new driving time, which is 20% less than his old driving time.
\(\frac{120}{\frac{5}{4}r}=\frac{4}{5}\cdot \frac{120}{r}\)
The above equation is an identity. Since r can be any positive number, we can't get a unique value to answer the original question. \(\implies\) Insufficient
Answer: A
Re: Khalil drove 120 kilometers in a certain amount of time. What was his
[#permalink]
21 Sep 2019, 16:41
21 Sep 2019, 16:41
8
Kudos
3
Bookmarks
given : \(vt = 120\)
from statement (1), \((v+5)(t-\frac{1}{3}) = 120\)
\(v + 5 = 15t = 15(\frac{120}{v})\)
so \(t = 3\) and \(v = 40\) ---> sufficient
from statement (2), \((\frac{5}{4})v*(\frac{4}{5})t = 120\) ---> no use because the fractions cancel each other (insufficient)
from statement (1), \((v+5)(t-\frac{1}{3}) = 120\)
\(v + 5 = 15t = 15(\frac{120}{v})\)
so \(t = 3\) and \(v = 40\) ---> sufficient
from statement (2), \((\frac{5}{4})v*(\frac{4}{5})t = 120\) ---> no use because the fractions cancel each other (insufficient)
