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21 Feb 2019, 12:52
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A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
35% (02:44) correct
65%
(02:37)
wrong
based on 128
sessions
History
Date
Time
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Not Attempted Yet
What is the tens digit of two-digit positive integer w?
(1) The tens digit of 2w is equal to the tens digit of w.
(2) The sum of the digits of w+5 is 5.
(1) The tens digit of 2w is equal to the tens digit of w.
(2) The sum of the digits of w+5 is 5.
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
eabhgoy
Joined: 12 Apr 2011
Last visit: 14 Jan 2021
Posts: 112
Given Kudos: 85
Location: United Arab Emirates
Concentration: Strategy, Marketing
Schools: CBS '21 Yale '21 INSEAD Jan'21 Intake IMD '21 (A)
GMAT 1: 670 Q50 V31
GMAT 2: 720 Q50 V37
GPA: 3.2
WE:Marketing (Telecommunications)
21 Feb 2019, 13:26
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kevincan
This took a while to solve!
from statement 1 we are told that 2*w and w share the same number in the tens digit.
now lets assume w is either from 10-20----90s or 19-29-39---99 series to test the extremes:
hence:
If w is:
10-20-30-40-50-60-70-80-90
2w will be:
20-40-60-80-100-120-140-160-180
or 2nd case:
w is
19-29-39-49-59-69-79-89-99
2w will be:
38-58-78-98-118-138-158-178-198
from the above we see only if w = 99 then 2w = 198 and satisfies the first statement. We also have other solutions such 95, 96, 97, 98, 99
Hence 1 is insufficient
Now in the second statement we are told: w+5 leads to a digit whose sum is 5.
Possible solutions are: 23, 32, 41, 50, 104
i.e. w = 18, 27, 36, 45, or 99
Again 2 is insufficient.
But if we combine 1 & 2 we get w=99
Hence both are required and C is the correct answer.
21 Feb 2019, 19:04
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eabhgoy
The question is asking for only the tens digit, so therefore 1 is sufficient and two is insufficient since 27 and 99 can both be possible solutions.
Therefore answer is A
