• 7 CATs FREE!
    If you earn 100 Forum Points

    Engage in the Beat The GMAT forums to earn
    100 points for $49 worth of Veritas practice GMATs FREE

    Veritas Prep
    VERITAS PRACTICE GMAT EXAMS
    Earn 10 Points Per Post
    Earn 10 Points Per Thanks
    Earn 10 Points Per Upvote
    REDEEM NOW
This topic has expert replies
User avatar
Elite Legendary Member
Posts: 3040
Joined: 24 Jul 2015
Location: Las Vegas, USA
Thanked: 19 times
Followed by:36 members
In a certain theater, the first row has 16 seats and the next row has 2 more seats than previous row. If the last row has 64 seats, what is the total number of seats?

A. 640
B. 720
C. 1,000
D. 1,200
E. 1,240


* A solution will be posted in two days.
Image
Math Revolution
Finish GMAT Quant Section with 10 minutes to spare.
The one-and-only World's First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Only $149 for 3 month Online Course
Free Resources-30 day online access & Diagnostic Test
Unlimited Access to over 120 free video lessons-try it yourself
Email to : info@mathrevolution.com

Master | Next Rank: 500 Posts
Posts: 126
Joined: 07 Jun 2014
Thanked: 3 times

by sandipgumtya » Thu Mar 17, 2016 9:02 am
We can apply AP series formula here.First term as 16 and last term 64.We get the no of terms as 25.Now the sum formula.
Sum=(25/2)*(2*16+24*2)=1000.Ans-C

Sandip.

User avatar
Elite Legendary Member
Posts: 3040
Joined: 24 Jul 2015
Location: Las Vegas, USA
Thanked: 19 times
Followed by:36 members

by Max@Math Revolution » Sat Mar 19, 2016 9:58 pm
In a certain theater, the first row has 16 seats and the next row has 2 more seats than previous row. If the last row has 64 seats, what is the total number of seats?

A. 640
B. 720
C. 1,000
D. 1,200
E. 1,240


A1=16, A2=16+2, A3=16+2*2,.....,An=16+(n-1)2=2n+14. In order make 2n+14=64, n should be 25. That is, there are 25 rows. Thus, in total, 25(16+64)/2=1,000 is derived. The answer is C.
Image
Math Revolution
Finish GMAT Quant Section with 10 minutes to spare.
The one-and-only World's First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
Only $149 for 3 month Online Course
Free Resources-30 day online access & Diagnostic Test
Unlimited Access to over 120 free video lessons-try it yourself
Email to : info@mathrevolution.com