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

Redeem

Fractions

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 124
Joined: Mon May 19, 2008 1:12 pm
Thanked: 3 times

Fractions

by Nycgrl » Tue Jul 01, 2008 5:54 pm
If R = 1+1/3+1/9+1/27 and S= 1+1/3*r , then s exceeds r by

(A) 1/3 (B)1/6 (C) 1/9 (D) 1/27 (E) 1/81

Any other methos to solve it without doing the actual calculation?
Top
Source: — Problem Solving |
Junior | Next Rank: 30 Posts
Posts: 28
Joined: Mon Jun 30, 2008 1:45 pm
Thanked: 3 times

by szapiszapo » Wed Jul 02, 2008 1:52 am
well... depends what you mean by calculation

R = 1 + 1/3 + 1/3 + 1/9 + 1/27
S = 1 + 1/3 * r

then S = 1 + 1/3 + 1/9 + 1/27 + 1/81


visually, we see that S exceeds R by 1/81, i.e. answer E
Top
Master | Next Rank: 500 Posts
Posts: 124
Joined: Mon May 19, 2008 1:12 pm
Thanked: 3 times

by Nycgrl » Wed Jul 02, 2008 3:44 am
Can you please explain
Top
Junior | Next Rank: 30 Posts
Posts: 28
Joined: Mon Jun 30, 2008 1:45 pm
Thanked: 3 times

by szapiszapo » Wed Jul 02, 2008 4:18 am
wording is:
R = 1 + 1/3 + 1/9 + 1/27
S = 1 + 1/3 * r

I just replace R in the equation forming S

therefore
S = 1 + 1/3 * ( 1 + 1/3 + 1/9 + 1/27)
S = 1 + 1/3*1 + 1/3*1/3 + 1/3*1/9 + 1/3*1/27
S = 1 + 1/(3*1) + 1/(3*3) + 1/(9*3) + 1/(27*3)
S = 1 + 1/3 + 1/9 + 1/27 + 1/81

S - R equals 1/81
Top
Post new topic Post Reply
• Page 1 of 1