NEW HERE? LEARN MORE
closeclose
Last visit was: 26 Apr 2024, 10:59 It is currently 26 Apr 2024, 10:59
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

John has to make two round trips to the grocery store by the same rout

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92948
Own Kudos [?]: 619208 [4]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
John has to make two round trips to the grocery store by the same rout [#permalink] New post   23 Jan 2018, 23:43
4
Bookmarks
Expert Reply
00:00
A
B
C
D
E

Difficulty:

65% (hard)

Question Stats:

67% (03:13) correct 33% (02:37) wrong based on 123 sessions
Hide Show timer Statistics
John has to make two round trips to the grocery store by the same route. On his initial trip to the store he travels at 20 miles per hour. He increases his speed on each of the following legs of the trip by 10 miles per hour. Which of the following is closest to his average speed in miles per hour for both round trips?

A. 31
B. 35
C. 39
D. 43
E. 44
ShowHide Answer
Official Answer
A
User avatar
B
rocko911
Manager
Manager
Joined: 11 Feb 2017
Posts: 161
Own Kudos [?]: 33 [0]
Given Kudos: 206
Send PM
Re: John has to make two round trips to the grocery store by the same rout [#permalink] New post   23 Jan 2018, 23:57
Bunuel wrote:
John has to make two round trips to the grocery store by the same route. On his initial trip to the store he travels at 20 miles per hour. He increases his speed on each of the following legs of the trip by 10 miles per hour. Which of the following is closest to his average speed in miles per hour for both round trips?

A. 31
B. 35
C. 39
D. 43
E. 44



A = 31

Total distance = D + D + D+ D
Total time = D/ 20 + D/30 + D/40 + D/50

Avg speed = Tot Distance / Tot time

= 31
User avatar
P
JeffTargetTestPrep
Target Test Prep Representative
Joined: 04 Mar 2011
Status:Head GMAT Instructor
Affiliations: Target Test Prep
Posts: 3043
Own Kudos [?]: 6277 [0]
Given Kudos: 1646
Send PM
Re: John has to make two round trips to the grocery store by the same rout [#permalink] New post   26 Jan 2018, 10:39
Expert Reply
Bunuel wrote:
John has to make two round trips to the grocery store by the same route. On his initial trip to the store he travels at 20 miles per hour. He increases his speed on each of the following legs of the trip by 10 miles per hour. Which of the following is closest to his average speed in miles per hour for both round trips?

A. 31
B. 35
C. 39
D. 43
E. 44


We can let the distance between his house and the store = 60 miles.

For his first trip to store, his speed is 20 mph; thus, the time = 60/20 = 3 hours.

For his first return trip home, his speed is 30 mph; thus, the time = 60/30 = 2 hours.

For his second trip to store, his speed is 40 mph; thus, the time = 60/40 = 1.5 hours.

Finally, for his second return trip home, his speed is 50 mph; thus, the time = 60/50 = 1.2 hours.

Recall that average speed = (total distance traveled)/(total time), so we have:

Avg speed = (60 + 60 + 60 + 60)/(3 + 2 + 1.5 + 1.2)

Avg speed = 240/7.7

Avg speed = 31.17 ≈ 31 mph

Answer: A
User avatar
B
Lodz697
Intern
Intern
Joined: 11 Oct 2023
Posts: 46
Own Kudos [?]: 12 [0]
Given Kudos: 96
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.77
Send PM
Re: John has to make two round trips to the grocery store by the same rout [#permalink] New post   13 Feb 2024, 08:40
Hi,

Here I used the correct procedure. However, I struggled with calculus.

Does anyone have suggestions for making calculus faster and easier in these types of questions?
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92948
Own Kudos [?]: 619208 [1]
Given Kudos: 81609
Send PM
CAT Tests Forum Quiz Mode
Re: John has to make two round trips to the grocery store by the same rout [#permalink] New post   13 Feb 2024, 10:08
1
Kudos
Expert Reply
Lodz697 wrote:
Hi,

Here I used the correct procedure. However, I struggled with calculus.

Does anyone have suggestions for making calculus faster and easier in these types of questions?

­

1. Arithmetic




How to Do Math on the GMAT Without Actually Doing Math
The Power of Estimation for GMAT Quant
How to Plug in Numbers on GMAT Math Questions
Number Sense for the GMAT
Can You Use a Calculator on the GMAT?
Why Approximate?
GMAT Math Strategies — Estimation, Rounding and other Shortcuts
The 4 Math Strategies Everyone Must Master, Part 1 (1. Test Cases and 2. Choose Smart Numbers.)
The 4 Math Strategies Everyone Must Master, part 2 (3. Work Backwards and 4. Estimate)
Intelligent Guessing on GMAT
How to Avoid Tedious Calculations on the Quantitative Section of the GMAT
GMAT Tip of the Week: No Calculator? No Problem.
The Importance of Sorting Answer Choices on the GMAT­


For more check Ultimate GMAT Quantitative Megathread

Hope it helps.­
GMAT Club Bot
gmatclubot
Re: John has to make two round trips to the grocery store by the same rout [#permalink]
13 Feb 2024, 10:08
Moderators:
Bunuel
Math Expert
92947 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions