Hi
Its easy to solve by plugging in numbers:
1. ab is a multiple of 3. You can take any two digit multiple of 3 starting from 12 onwards and you will see that in all the cases
a+b is also divisible by 3. SUFF
2. a-2b=divisible by 3;again you can plug in numbers such as
7-2(2)=3; a=7 b=2 and 7+2=9 ----->multiple of 3
5-2(1)=3; a=5 b=1 and 5+1=6 ----->multiple of 3
SUFF
Hence D. HTH
Help
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Source: Beat The GMAT — Data Sufficiency |
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DeepthiRajan
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Statement 1: From the rule of divisibility by 3, we can easily conclude that if the two-digit number "ab" (where a is in the tens place and b is in the ones place) is a multiple of 3, then (a + b) is also a multiple of 3.GHong14 wrote:If a and b are both single-digit positive integers, is a + b a multiple of 3?
(1) The two-digit number "ab" (where a is in the tens place and b is in the ones place) is a multiple of 3.
(2) a - 2b is a multiple of 3.
Sufficient
Statement 2: a - 2b is a multiple of 3
Now we can write (a - 2b) as (a + b - 3b).
Thus (a + b - 3b) is a multiple of 3, which is obtained by subtracting 3b (which is also multiple of 3) from (a + b).
Hence, (a + b) is also a multiple of 3.
Sufficient
The correct answer is D.
Rahul Lakhani
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Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
