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The sequence of four numbers a1, a2 , a3 and a4 is such that
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18 May 2013, 01:25
2
7
00:00
A
B
C
D
E
Difficulty:
15% (low)
Question Stats:
76% (00:47) correct 24% (01:12) wrong based on 351 sessions
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The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
Re: The sequence of four numbers a1, a2 , a3 and a4 is such that
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18 May 2013, 01:37
1
The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
Re: The sequence of four numbers a1, a2 , a3 and a4 is such that
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18 May 2013, 05:10
pritishmohan wrote:
The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
1. \(a_2=15\)
2. \(a_4 = 29\)
given:- a2 - a1 = a1 - 1 => a2 = 2a1 - 1
similarly we can get a3 = 3a1 - 2 and a4 = 4a1 - 3.
AD/BCE
statement 1:- a2 = 15 => 2a1 - 1 = 15.So we can get the value of a1. A alone is sufficient BCE out.
statement2:- a4 = 29 => 4a1-3 = 29 .So we can get the value of a1. B alone is sufficient.
Answer is D
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Re: The sequence of four numbers a1, a2 , a3 and a4 is such that
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19 May 2013, 04:35
pritishmohan wrote:
The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
1. \(a_2=15\)
2. \(a_4 = 29\)
From the given information, we know that \(a_n = a_{n-1} + (a_1 - 1) = na_1 - (n - 1)\)
Re: The sequence of four numbers a1, a2 , a3 and a4 is such that
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19 May 2013, 04:40
3
pritishmohan wrote:
The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
Re: The sequence of four numbers a1, a2 , a3 and a4 is such that
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30 Oct 2014, 02:52
1
1
alexa wrote:
Bunuel please solve this question, I don't understand the solution for statement #2.
Thank you!
The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
Each number after the first is \(a_1-1\) greater than preceding number means that: \(a_2=a_1+(a_1-1)=2a_1-1\) \(a_3=a_2+(a_1-1)=3a_1-2\) \(a_4=a_3+(a_1-1)=4a_1-3\)
(1) \(a_2=15\). We can find \(a_1\). Sufficient.
(2) \(a_4 = 29\). We can find \(a_1\). Sufficient.
The sequence of four numbers a1, a2 , a3 and a4 is such that
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12 Nov 2015, 04:25
pritishmohan wrote:
The sequence of four numbers \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) is such that each number after the first is \(a_1-1\) greater than preceding number . What is the value of \(a_1\)?
(1) \(a_2=15\)
(2) \(a_4 = 29\)
Given: \(a_1\), \(a_2\) , \(a_3\) and \(a_4\) and \(a_2\) = \(a_1\) + \(a_1-1\) - (i) \(a_3\) = \(a_1\) + 2\(a_1-1\) - (ii) \(a_4\) = \(a_1\) + 3\(a_1-1\) - (iii)
Required: \(a_1\) = ?
Statement 1: \(a_2=15\) Using (i) we can find the value of \(a_1\) SUFFICIENT
Statement 2: \(a_4 = 29\) Using (iii), we can find the value of \(a_1\) SUFFICIENT
Hence Option D
Note: You do not need to solve for the values of \(a_1\). This can save precious time on the test.
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76% (00:47) correct 
