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31 Jan 2024, 02:30
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B
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:
57% (01:28) correct
43%
(01:06)
wrong
based on 96
sessions
History
Date
Time
Result
Not Attempted Yet
What is the units digit of a positive integer n?
(1) The units digit of n^2 is 4
(2) The units digit of n^3 is 8
(1) The units digit of n^2 is 4
(2) The units digit of n^3 is 8
Pure algebraic questions like this one are no longer part of the GMAT Data Sufficiency syllabus.
For relevant Data Sufficiency questions, please check the Data Sufficiency forum:
Data Sufficiency Forum
Data Sufficiency Forum
31 Jan 2024, 02:55
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The answer to this should be option (B)
If we consider option (A), we can see that unit's digit ending with both 2 & 8 yield the unit's digit as 4 when squared.
Since we cannot definitely determine the value hence (A) is incorrect & hence by default (D) is incorrect.
If we consider option (B) alone, then only a number having unit's digit as 2 will yield unit's digit as 8 when cubed.
Hence the answer is (B)
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If we consider option (A), we can see that unit's digit ending with both 2 & 8 yield the unit's digit as 4 when squared.
Since we cannot definitely determine the value hence (A) is incorrect & hence by default (D) is incorrect.
If we consider option (B) alone, then only a number having unit's digit as 2 will yield unit's digit as 8 when cubed.
Hence the answer is (B)
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31 Jan 2024, 05:43
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Option B
odd unit's digit is clearly out of our way for a ^2to have 4 or a ^3 to have 8 as unit's digit.
To analyse statement 1:
Multiple options (2 and 8) have unit's digit as 4, not sufficient.
To analyse statement 2:
Only 1 option which is 2. Hence, Sufficient.
So Statement 2 alone is sufficient but not statement 1.
Correct option should be B
odd unit's digit is clearly out of our way for a ^2to have 4 or a ^3 to have 8 as unit's digit.
To analyse statement 1:
| Unit's Digit | Unit's digit after ^2 |
| 2 | 4 |
| 4 | 6 |
| 6 | 6 |
| 8 | 4 |
Multiple options (2 and 8) have unit's digit as 4, not sufficient.
To analyse statement 2:
| Unit's Digit | Unit's digit after ^3 |
| 2 | 8 |
| 4 | 4 |
| 6 | 6 |
| 8 | 2 |
Only 1 option which is 2. Hence, Sufficient.
So Statement 2 alone is sufficient but not statement 1.
Correct option should be B
