Fastest way to solve this one? 161) 2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 Answer is A. a. 2^9 b. 2^10 c. 2^16 d. 2^35 e. 2^37

Start by taking out 2 as common.... as below : 2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 = 2( 1 + 1 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 ) = 2 (2+2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 ) = 2^ 2 ( 1+1+2+2^2 + 2^3 + 2^4 + 2^5 + 2^6) .............the rest of the steps can be orally counted (seeing the trend) ans is 2^9

pkw209 wrote:Fastest way to solve this one? 161) 2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 Answer is A. a. 2^9 b. 2^10 c. 2^16 d. 2^35 e. 2^37 You can also do it by pattern recognition 2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 =2^2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 2^2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 =2^3 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 2^3 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 = 2^4 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 and so on to get 2^9

pkw209 wrote:Fastest way to solve this one? 161) 2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 +2^8 Answer is A. a. 2^9 b. 2^10 c. 2^16 d. 2^35 e. 2^37 It can be considered as a sum of a geometric progression (2, 2^2, 2^4... 2^8) and 2 Sum of n elements in a GP is a(r^n - 1)/(r-1) in this case 2(2^8-)/(2-1) = 2^9-2 and adding the first 2 which we omitted we get 2^9

GMAT PREP adding exponents - The Beat The GMAT Forum - Expert GMAT Help & MBA Admissions Advice

GMATLiveTeachStarts Nov 22

LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow: Sun · 9:30 AM to 12:30 PM ET
Included: 40 hours of live online classes + 6 months of TTP OnDemand

Attend the first class for free
Every class is recorded, so you never fall behind

View classes & enroll

Limited seats available

EALiveTeachOnDemandStart anytime

EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee

$05-day trial no automatic billing

Schedule
Included: 40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.

165+ EA Score Guarantee
4,100+ Quant, Verbal, and Integrated Reasoning practice questions
400+ hours of in-depth video lessons
3,000+ step-by-step video solutions

View EA class & enroll Start free 5-day trial

Limited cohort · enrollment openTrial includes full course access

GMATOnDemandStart anytime

SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee

$0to start then $127/mo

Personalized study plan and analytics
Thousands of lessons and practice questions

Start free 5-day trial

Read 563 reviews

Choose how you want to prepare

Get Ready for GMAT Test Day Faster with Live Online Classes

Target Test Prep EA OnDemand

Target Test Prep GMAT OnDemand

GMAT PREP adding exponents

GMAT/MBA Expert

Chicago Booth

GMAT Course Reviews

Admissions Consulting Reviews

FREE GMAT PREP RESOURCES

GMAT PREP DEAL TRACKER