GRE Prep Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Sequence S is such that Sn
[#permalink]
02 Mar 2018, 03:32
02 Mar 2018, 03:32
1
Expert Reply
1
Bookmarks
00:00
Question Stats:
71% (02:12) correct
28% (02:30) wrong based on 122 sessions
Hide Show timer Statistics
Sequence S is such that \(S_n = S_{n-1} + \frac{3}{2}\) and \(S_1 = 2\)
Sequence A is such that \(A_n = A_{n-1} - 1.5\) and \(A_1 = 18.5\)
A. The quantity in Column A is greater
B. The quantity in Column B is greater
C. The two quantities are equal
D. The relationship cannot be determined from the information given
Kudos for the correct answer AND explanation
Sequence A is such that \(A_n = A_{n-1} - 1.5\) and \(A_1 = 18.5\)
Quantity A |
Quantity B |
The sum of the terms in \(S\) from \(S_1\) to \(S_{13}\), inclusive |
The sum of the terms from in \(A\) from \(A_1\) to \(A_{13}\), inclusive |
A. The quantity in Column A is greater
B. The quantity in Column B is greater
C. The two quantities are equal
D. The relationship cannot be determined from the information given
Kudos for the correct answer AND explanation
Re: Sequence S is such that Sn
[#permalink]
02 Mar 2018, 10:03
02 Mar 2018, 10:03
7
1
Bookmarks
Formula given to us:
\(Sn = Sn-1 +1.5; s1 = 2 and
An = An-1 - 1.5; A1 = 18.5\)
For the first sequence
Each subsequent value of \(s\) is greater by \(1.5\) For solving the question we need to calculate the sum of first 13 terms
we have the 1st term as \(2\). There remains \(12\) more terms. We know that there is an increase of \(1.5\) per term hence there is a total increase of \(12 * 1.5 = 18\)
Last term of the sequence = \(2+18 = 20\)
Since the sequence is equally spaced avg = \(\frac{2 +20}{2} = 11\)
There are a total of \(13\) terms hence sum of the sequence = \(11* 13 = 143\)
For the second sequence
Each subsequent value of A is less by \(1.5\) For solving the question we need to calculate the sum of first \(13\) terms
we have the 1st term as \(18.5\) There remains \(12\) more terms. We know that there is a decrease of \(1.5\) per term hence there is a total decrease of \(12 * 1.5 = 18\)
Last term of the sequence = \(18.5 - 18 = 0.5\)
Since the sequence is equally spaced avg = \(\frac{0.5 +18.5}{2} = 9.5\)
There are a total of \(13\) terms hence sum of the sequence = \(9.5* 13 = 123.5\)
Option A
\(Sn = Sn-1 +1.5; s1 = 2 and
An = An-1 - 1.5; A1 = 18.5\)
For the first sequence
Each subsequent value of \(s\) is greater by \(1.5\) For solving the question we need to calculate the sum of first 13 terms
we have the 1st term as \(2\). There remains \(12\) more terms. We know that there is an increase of \(1.5\) per term hence there is a total increase of \(12 * 1.5 = 18\)
Last term of the sequence = \(2+18 = 20\)
Since the sequence is equally spaced avg = \(\frac{2 +20}{2} = 11\)
There are a total of \(13\) terms hence sum of the sequence = \(11* 13 = 143\)
For the second sequence
Each subsequent value of A is less by \(1.5\) For solving the question we need to calculate the sum of first \(13\) terms
we have the 1st term as \(18.5\) There remains \(12\) more terms. We know that there is a decrease of \(1.5\) per term hence there is a total decrease of \(12 * 1.5 = 18\)
Last term of the sequence = \(18.5 - 18 = 0.5\)
Since the sequence is equally spaced avg = \(\frac{0.5 +18.5}{2} = 9.5\)
There are a total of \(13\) terms hence sum of the sequence = \(9.5* 13 = 123.5\)
Option A
