BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

exponents-Gprep

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 447
Joined: Sun Apr 19, 2009 9:08 pm
Location: Kolkata,India
Thanked: 7 times
GMAT Score:670

exponents-Gprep

by uptowngirl92 » Tue Nov 03, 2009 3:47 am
What is the value of 2 + 2 + 2^2 + 2^3 + 2^4 + 2^5 + 2^6 + 2^7 + 2^8? [/b}

Got the correct ans by the long long long approach..Shorter way??
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 124
Joined: Thu Jun 18, 2009 5:33 am
Thanked: 35 times

by NikolayZ » Tue Nov 03, 2009 5:26 am
Hey uptowngirl!

Look at the part 2+2. It is 4, right ? or 2^2.
Hence, we can factor 2^2 from two first figures.
i mean
[2^2+2^2]+2^3...=2^2(1+1)+2^3.....=2*2^2+2^3...=2^3+2^3+2^4...

Notice since that moment factoring 2^n will result in increasing of the next number's power by 1 at a time.
4 5 6 7 8 9 ===> 2^9 is your answer.
Top
Post new topic Post Reply
• Page 1 of 1