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

 It is currently 24 Mar 2019, 04:12

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

A parking lot contains ten cars. The average age of the cars is seven

Author Message
TAGS:

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 53798
A parking lot contains ten cars. The average age of the cars is seven  [#permalink]

Show Tags

13 Feb 2019, 00:48
00:00

Difficulty:

15% (low)

Question Stats:

82% (00:59) correct 18% (01:26) wrong based on 34 sessions

HideShow timer Statistics

A parking lot contains ten cars. The average age of the cars is seven years. If the average age of nine of the cars is six years, what is the age of the remaining car in years?

(A) 3
(B) 7
(C) 10
(D) 16
(E) 20

_________________
SVP
Joined: 18 Aug 2017
Posts: 2454
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: A parking lot contains ten cars. The average age of the cars is seven  [#permalink]

Show Tags

13 Feb 2019, 06:55
Bunuel wrote:
A parking lot contains ten cars. The average age of the cars is seven years. If the average age of nine of the cars is six years, what is the age of the remaining car in years?

(A) 3
(B) 7
(C) 10
(D) 16
(E) 20

age of all cars = 70
and 9 cars age = 54
70-54 = 16
IMO D
_________________

If you liked my solution then please give Kudos. Kudos encourage active discussions.

Manager
Joined: 18 Oct 2018
Posts: 68
Location: India
GPA: 4
Re: A parking lot contains ten cars. The average age of the cars is seven  [#permalink]

Show Tags

13 Feb 2019, 07:06
Since average age of 10 cars= 7 years,
Thus,sum of ages of all the 10 cars = 10*7= 70 years
Average age of 9 cars= 6 years
Sum of ages of the 9 cars= 9*6=54 years.
Hence,the age of the 10th car=70-54=16 years

Posted from my mobile device
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4404
Location: India
GPA: 3.5
Re: A parking lot contains ten cars. The average age of the cars is seven  [#permalink]

Show Tags

13 Feb 2019, 08:06
Bunuel wrote:
A parking lot contains ten cars. The average age of the cars is seven years. If the average age of nine of the cars is six years, what is the age of the remaining car in years?

(A) 3
(B) 7
(C) 10
(D) 16
(E) 20

$$10*7 - 6*9$$

= $$70 - 54$$

= 16, Answer must be $$(D) 16$$
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 5409
Location: United States (CA)
Re: A parking lot contains ten cars. The average age of the cars is seven  [#permalink]

Show Tags

15 Feb 2019, 18:25
Bunuel wrote:
A parking lot contains ten cars. The average age of the cars is seven years. If the average age of nine of the cars is six years, what is the age of the remaining car in years?

(A) 3
(B) 7
(C) 10
(D) 16
(E) 20

The total sum of the ages of all 10 cars is 10 x 7 = 70.

The sum of the 9 cars is 9 x 6 = 54

Therefore, the age of the remaining car is 70 - 54 = 16.

_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

GMAT Tutor
Joined: 24 Jun 2008
Posts: 1395
Re: A parking lot contains ten cars. The average age of the cars is seven  [#permalink]

Show Tags

16 Feb 2019, 16:52
It's a weighted average problem so you can also use a number line:

--6--7-----------------C---

The ratio of the distances to the middle must be 1 to 9, since that's the ratio of the numbers of cars in each group, and since the smaller distance is 1, the larger distance is 9, and C = 7+9 = 16.

Of course with a problem set up in such a straightforward way, you don't need to use a weighted average method to solve - the methods posted above are just as easy.
_________________

GMAT Tutor in Toronto

If you are looking for online GMAT math tutoring, or if you are interested in buying my advanced Quant books and problem sets, please contact me at ianstewartgmat at gmail.com

Re: A parking lot contains ten cars. The average age of the cars is seven   [#permalink] 16 Feb 2019, 16:52
Display posts from previous: Sort by