If the sum of the interior angles of a regular polygon...

This topic has expert replies
Moderator
Posts: 2237
Joined: Sun Oct 29, 2017 2:08 pm
Followed by:2 members
If the sum of the interior angles of a regular polygon measures up to 1440 degrees, how many sides does the polygon have?

A. 10 sides
B. 8 sides
C. 12 sides
D. 9 sides
E. None of these

The OA is A.

I know that exist a formula to determine the number of sides 180(n-2) but is there another way to solve this PS question? Can any experts help, please? Thanks!

User avatar
Master | Next Rank: 500 Posts
Posts: 103
Joined: Mon Jun 23, 2014 11:31 pm
Thanked: 25 times
Followed by:12 members
GMAT Score:770

by BestGMATEliza » Fri Jan 19, 2018 10:05 am
I think the easiest way to solve this problem is to use the formula:
(n-2)*180=1440
1440/180=8=n-2
Therefore n=10
Eliza Chute
Best GMAT Prep Courses
GMAT course comparison and reviews
Your one stop for all your GMAT studying needs!

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Fri Jan 19, 2018 6:50 pm
Hi AAPL,

We're told that the sum of the interior angles of a regular polygon totals 1440 degrees. We're asked for the number of sides that the polygon has. There is one essential math rule that is required to answer this question - but there are a couple of different ways to consider the rule.

I often view the rule as "add a side, add 180 degrees"

3-sides = 180 degrees
4-sides = 360 degrees
5-sides = 540 degrees
6-sides = 720 degrees
Etc.

In this way, you just have to add 180s until you hit a total of 1440...Once you do that, you'll have the correct answer.

Final Answer: A

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 7223
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Mon Feb 05, 2018 9:46 am
AAPL wrote:If the sum of the interior angles of a regular polygon measures up to 1440 degrees, how many sides does the polygon have?

A. 10 sides
B. 8 sides
C. 12 sides
D. 9 sides
E. None of these
We can let n = the number of sides of the polygon and use the formula for the sum of the interior angles:

1440 = 180(n - 2)

1440 = 180n - 360

1800 = 180n

10 = n

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage