If a=(1/21)+(1/22)+(1/23)+(1/24)+(1/25)+(1/26)+(1/27)+(1/28)+(1/29)+(1/30). What is the value of a?
(A) 0.15 < a < 0.25
(B) 0.25 < a < 0.35
(C) 0.35 < a < 0.45
(D) 0.45 < a < 0.55
(E) 0.55 < a < 0.65
OA=C
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
(1/21)+(1/22)+(1/23)+(1/24)+(1/25)+(1/26)+(1/27)+(1/28)+(1/2
This topic has expert replies
-
hazelnut01
- Master | Next Rank: 500 Posts
- Posts: 157
- Joined: Sat Nov 19, 2016 5:34 am
- Thanked: 2 times
- Followed by:4 members
-
GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
Determine the RANGE of the sum.ziyuenlau wrote:If a=(1/21)+(1/22)+(1/23)+(1/24)+(1/25)+(1/26)+(1/27)+(1/28)+(1/29)+(1/30). What is the value of a?
(A) 0.15 < a < 0.25
(B) 0.25 < a < 0.35
(C) 0.35 < a < 0.45
(D) 0.45 < a < 0.55
(E) 0.55 < a < 0.65
There are 10 fractions in total.
The smallest fraction is 1/30.
The greatest fraction is 1/21.
If all 10 fractions were 1/30, then a = 10(1/30) = 1/3 ≈ 0.33.
Since 9 of the fractions are actually GREATER THAN 1/30, a must be GREATER THAN 0.33.
If all 10 fractions were 1/20, then 1 = 10(1/20) = 1/2 = 0.5.
Since all 10 fractions are actually LESS THAN 1/20, a must be LESS THAN 0.5.
Thus:
0.33 < a < 0.5.
Of the five answer choices, the closest match to the range in blue is C.
The correct answer is C.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
GMAT/MBA Expert
-
Brent@GMATPrepNow
- GMAT Instructor
- Posts: 16207
- Joined: Mon Dec 08, 2008 6:26 pm
- Location: Vancouver, BC
- Thanked: 5254 times
- Followed by:1268 members
- GMAT Score:770
Here's a similar question to practice with: https://www.beatthegmat.com/m-is-the-sum ... 94397.html
Cheers,
Brent
Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
