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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
Posts: 10148
Given Kudos: 4
GMAT 1: 760 Q51 V42
GPA: 3.82
What is the scope including 1/11+1/12+1/13+......+1/20?
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24 Jul 2016, 03:09
24 Jul 2016, 03:09
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Expert Reply
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A
B
C
D
E
Difficulty:
35%
(medium)
Question Stats:
68% (01:20) correct
32%
(01:38)
wrong
based on 186
sessions
What is the scope including 1/11+1/12+1/13+......+1/20?
A 1/6~1/5
B. 1/5~1/4
C. 1/4~1/3
D. 1/3~1/2
E. 1/2~1
*An answer will be posted in 2 days.
A 1/6~1/5
B. 1/5~1/4
C. 1/4~1/3
D. 1/3~1/2
E. 1/2~1
*An answer will be posted in 2 days.
Re: What is the scope including 1/11+1/12+1/13+......+1/20?
[#permalink]
24 Jul 2016, 05:29
24 Jul 2016, 05:29
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Expert Reply
MathRevolution wrote:
What is the scope including 1/11+1/12+1/13+......+1/20?
A 1/6~1/5
B. 1/5~1/4
C. 1/4~1/3
D. 1/3~1/2
E. 1/2~1
*An answer will be posted in 2 days.
A 1/6~1/5
B. 1/5~1/4
C. 1/4~1/3
D. 1/3~1/2
E. 1/2~1
*An answer will be posted in 2 days.
For Maximum value : It should be less than 1/11 + 1/11 +1/11... 10 times = 10/11 ~ 1
For Minimum Value : It should be greater than 1/20+ 1/2-+ 1/20 .. 10 times = 10/20 = 1/2.
Thus, the answer should lie between 1/2 and 1. Correct ans : E.
Re: What is the scope including 1/11+1/12+1/13+......+1/20?
[#permalink]
25 Jul 2016, 11:38
25 Jul 2016, 11:38
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If you want a more precise answer:
You know there are 10 numbers and first value is \(\frac{1}{11}\) and last value is \(\frac{1}{20}\)
So
\(Avg = \frac{First + Last}{2} = \frac{31}{440}\)
Then
\(Sum = Avg * n = \frac{31}{440}*10 =\frac{31}{44} \approx{\frac{3}{4}}\)
Answer E.
You know there are 10 numbers and first value is \(\frac{1}{11}\) and last value is \(\frac{1}{20}\)
So
\(Avg = \frac{First + Last}{2} = \frac{31}{440}\)
Then
\(Sum = Avg * n = \frac{31}{440}*10 =\frac{31}{44} \approx{\frac{3}{4}}\)
Answer E.
