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07 Mar 2018, 03:41
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D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
55%
(hard)
Question Stats:
68% (02:28) correct
32%
(03:01)
wrong
based on 302
sessions
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[GMAT math practice question]
The terms of the sequence {An}, where n is a positive integer, satisfy A1=81, A2=82, A3=83, and An+3=An+4. Which of the following cannot be a value of An?
A. 801
B. 802
C. 803
D. 804
E. 805
The terms of the sequence {An}, where n is a positive integer, satisfy A1=81, A2=82, A3=83, and An+3=An+4. Which of the following cannot be a value of An?
A. 801
B. 802
C. 803
D. 804
E. 805
Sequence = 81,82,83, 85,86,87, 89,90,91, 93,94,95, 97,98,99, 101,102,102,..
Every 4th number is missing :After every 3 numbers, the number jumpy by 2 :
so we don't have 84,92,96,100,..... : This is in AP with an increment of 4.
So we know numbers divisible by 4 cannot be there in the given series
Test the numbers :
1. 801 - This is not divisible by 4
2. 802 - This is not divisible by 4
3. 803 - This is not divisible by 4
4. 804 - This is divisible by 4
5. 805 - This is not divisible by 4
Every 4th number is missing :After every 3 numbers, the number jumpy by 2 :
so we don't have 84,92,96,100,..... : This is in AP with an increment of 4.
So we know numbers divisible by 4 cannot be there in the given series
Test the numbers :
1. 801 - This is not divisible by 4
2. 802 - This is not divisible by 4
3. 803 - This is not divisible by 4
4. 804 - This is divisible by 4
5. 805 - This is not divisible by 4
General Discussion
09 Mar 2018, 00:22
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=>
The terms of the sequence can be divided into three groups:
A1 = 81, A4 = 85, A7 = 89, … : These have a remainder of 1 when they are divided by 4.
A2 = 82, A5 = 86, A8 = 90, … : These have a remainder of 2 when they are divided by 4.
A3 = 83, A6 = 87, A9 = 91, … : These have a remainder of 3 when they are divided by 4.
No term of the sequence is a multiple of 4.
Since 804 is a multiple of 4, it cannot be a term of the sequence.
Therefore, the answer is D.
Answer: D
The terms of the sequence can be divided into three groups:
A1 = 81, A4 = 85, A7 = 89, … : These have a remainder of 1 when they are divided by 4.
A2 = 82, A5 = 86, A8 = 90, … : These have a remainder of 2 when they are divided by 4.
A3 = 83, A6 = 87, A9 = 91, … : These have a remainder of 3 when they are divided by 4.
No term of the sequence is a multiple of 4.
Since 804 is a multiple of 4, it cannot be a term of the sequence.
Therefore, the answer is D.
Answer: D
