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

 It is currently 20 Feb 2019, 15:43

### 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

## Events & Promotions

###### Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
• ### Free GMAT Prep Hour

February 20, 2019

February 20, 2019

08:00 PM EST

09:00 PM EST

Strategies and techniques for approaching featured GMAT topics. Wednesday, February 20th at 8 PM EST

February 21, 2019

February 21, 2019

10:00 PM PST

11:00 PM PST

Kick off your 2019 GMAT prep with a free 7-day boot camp that includes free online lessons, webinars, and a full GMAT course access. Limited for the first 99 registrants! Feb. 21st until the 27th.

# What is the circumference of a circle whose area is 49π?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 53020
What is the circumference of a circle whose area is 49π?  [#permalink]

### Show Tags

17 Jan 2019, 03:48
00:00

Difficulty:

5% (low)

Question Stats:

94% (00:36) correct 6% (00:20) wrong based on 25 sessions

### HideShow timer Statistics

What is the circumference of a circle whose area is 49π?

A 7π
B 14π
C 24.5π
D 35π
E 49π

_________________
VP
Joined: 09 Mar 2018
Posts: 1001
Location: India
Re: What is the circumference of a circle whose area is 49π?  [#permalink]

### Show Tags

17 Jan 2019, 04:07
Bunuel wrote:
What is the circumference of a circle whose area is 49π?

A 7π
B 14π
C 24.5π
D 35π
E 49π

Area = 49 π
π r^2 = 49 π
r = 7

C = 2π7
C =14 π

_________________

If you notice any discrepancy in my reasoning, please let me know. Lets improve together.

Quote which i can relate to.
Many of life's failures happen with people who do not realize how close they were to success when they gave up.

e-GMAT Representative
Joined: 04 Jan 2015
Posts: 2581
Re: What is the circumference of a circle whose area is 49π?  [#permalink]

### Show Tags

17 Jan 2019, 05:35

Solution

Given:
• Area of the circle = 49ᴨ

To find:
• The circumference of the circle

Approach and Working:
Area = $$ᴨr^2 = 49ᴨ$$
• Implies, $$r^2 = 49$$
• Thus, r = 7

Circumference = 2ᴨr = 2ᴨ * 7 = 14ᴨ

Hence, the correct answer is Option B

_________________

| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

Manager
Joined: 15 Feb 2018
Posts: 244
Re: What is the circumference of a circle whose area is 49π?  [#permalink]

### Show Tags

19 Jan 2019, 18:23
Finding area from circumference seems to be asked frequently, so it can't hurt to learn the formula

$$Area = \frac{C^2}{(4π)}$$

We are given that A=49π

$$49π = \frac{C^2}{(4π)}$$
$$49π·4π = C^2$$
$$7^2·2^2·π^2=C^2$$
$$7·2·π=C=14π$$
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4387
Location: India
GPA: 3.5
Re: What is the circumference of a circle whose area is 49π?  [#permalink]

### Show Tags

20 Jan 2019, 01:54
Bunuel wrote:
What is the circumference of a circle whose area is 49π?

A 7π
B 14π
C 24.5π
D 35π
E 49π

$$πr^2 = 49π$$

So, $$r = 7$$

Thus, the circumference will be $$2*π*7 = 14π$$ , Answer must be (B) 14π
_________________

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 )

Re: What is the circumference of a circle whose area is 49π?   [#permalink] 20 Jan 2019, 01:54
Display posts from previous: Sort by