Symbols and Operator

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Source: — Data Sufficiency |

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by bluementor » Mon May 11, 2009 2:36 am
∆ could be addition, subtraction, multiplication or division.

what is 1 ∆ 2?

Statement 1: n ∆ 0 = n

so ∆ could only be addition or subtraction.

if ∆ = addition, then 1 ∆ 2 = 3
if ∆ = subtraction, then 1 ∆ 2 = -1. Insufficient.

Statement 2: n ∆ n = 0 for all integers n.

so ∆ could only be subtraction. hence, 1 ∆ 2 = -1. Sufficient.

Choose B. What's the OA?

-BM-

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by California4jx » Mon May 11, 2009 3:57 am
bluementor wrote:∆ could be addition, subtraction, multiplication or division.

what is 1 ∆ 2?

Statement 1: n ∆ 0 = n

so ∆ could only be addition or subtraction.

if ∆ = addition, then 1 ∆ 2 = 3
if ∆ = subtraction, then 1 ∆ 2 = -1. Insufficient.

Statement 2: n ∆ n = 0 for all integers n.

so ∆ could only be subtraction. hence, 1 ∆ 2 = -1. Sufficient.

Choose B. What's the OA?

-BM-
the answer is B - but why cant we pick n to be 0 in second statement and that will make Addition, Multiplicaton to be true as well ?? --- that is where I fell down

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by sacx » Mon May 11, 2009 4:54 am
California4jx wrote:
bluementor wrote:∆ could be addition, subtraction, multiplication or division.

what is 1 ∆ 2?

Statement 1: n ∆ 0 = n

so ∆ could only be addition or subtraction.

if ∆ = addition, then 1 ∆ 2 = 3
if ∆ = subtraction, then 1 ∆ 2 = -1. Insufficient.

Statement 2: n ∆ n = 0 for all integers n.

so ∆ could only be subtraction. hence, 1 ∆ 2 = -1. Sufficient.

Choose B. What's the OA?

-BM-
the answer is B - but why cant we pick n to be 0 in second statement and that will make Addition, Multiplicaton to be true as well ?? --- that is where I fell down
the second statement is 'n ∆ n = 0 for all integers n'. so the statement has to be true for all integers not just 0.
SACX

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by California4jx » Mon May 11, 2009 5:45 am
sacx wrote:
California4jx wrote:
bluementor wrote:∆ could be addition, subtraction, multiplication or division.

what is 1 ∆ 2?

Statement 1: n ∆ 0 = n

so ∆ could only be addition or subtraction.

if ∆ = addition, then 1 ∆ 2 = 3
if ∆ = subtraction, then 1 ∆ 2 = -1. Insufficient.

Statement 2: n ∆ n = 0 for all integers n.

so ∆ could only be subtraction. hence, 1 ∆ 2 = -1. Sufficient.

Choose B. What's the OA?

-BM-
the answer is B - but why cant we pick n to be 0 in second statement and that will make Addition, Multiplicaton to be true as well ?? --- that is where I fell down
the second statement is 'n ∆ n = 0 for all integers n'. so the statement has to be true for all integers not just 0.
exactly, it has to be true for all integers including 0 !! -- why in the above explanaton are we missing 0 and just consider integers above 0 ... I understand the stmt B is true for SUB when we disregard 0 ---- but as u said its for all integers -- and if u consider 0 - then ADD, MUL supports STMT 2 --

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by sacx » Mon May 11, 2009 9:02 pm
California4jx wrote:
sacx wrote:
California4jx wrote:
bluementor wrote:∆ could be addition, subtraction, multiplication or division.

what is 1 ∆ 2?

Statement 1: n ∆ 0 = n

so ∆ could only be addition or subtraction.

if ∆ = addition, then 1 ∆ 2 = 3
if ∆ = subtraction, then 1 ∆ 2 = -1. Insufficient.

Statement 2: n ∆ n = 0 for all integers n.

so ∆ could only be subtraction. hence, 1 ∆ 2 = -1. Sufficient.

Choose B. What's the OA?

-BM-
the answer is B - but why cant we pick n to be 0 in second statement and that will make Addition, Multiplicaton to be true as well ?? --- that is where I fell down
the second statement is 'n ∆ n = 0 for all integers n'. so the statement has to be true for all integers not just 0.
exactly, it has to be true for all integers including 0 !! -- why in the above explanaton are we missing 0 and just consider integers above 0 ... I understand the stmt B is true for SUB when we disregard 0 ---- but as u said its for all integers -- and if u consider 0 - then ADD, MUL supports STMT 2 --
Let me give you couple of examples

1. Subtraction
when n =0, n ∆ n = 0
when n = 1, n ∆ n = 0
when n = -3, n ∆ n = 0

For all integers, n ∆ n = 0

2. multiplication
when n = 0, n ∆ n = 0
when n= 1, n ∆ n = 1
when n= -2, n ∆ n = 4

we can clearly see that n ∆ n is only true when n = 0

3. division

when n = 0, n ∆ n = 0
when n= 1, n ∆ n = 1
when n= -2, n ∆ n = 1

true only when n = 0

4. addition

when n = 0, n ∆ n = 0
when n= 1, n ∆ n = 2
when n= -2, n ∆ n = -4

again true only when n = 0.
SACX

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by California4jx » Tue May 12, 2009 4:46 am
sacx wrote:
California4jx wrote:
sacx wrote:
California4jx wrote:
bluementor wrote:∆ could be addition, subtraction, multiplication or division.

what is 1 ∆ 2?

Statement 1: n ∆ 0 = n

so ∆ could only be addition or subtraction.

if ∆ = addition, then 1 ∆ 2 = 3
if ∆ = subtraction, then 1 ∆ 2 = -1. Insufficient.

Statement 2: n ∆ n = 0 for all integers n.

so ∆ could only be subtraction. hence, 1 ∆ 2 = -1. Sufficient.

Choose B. What's the OA?

-BM-
the answer is B - but why cant we pick n to be 0 in second statement and that will make Addition, Multiplicaton to be true as well ?? --- that is where I fell down
the second statement is 'n ∆ n = 0 for all integers n'. so the statement has to be true for all integers not just 0.
exactly, it has to be true for all integers including 0 !! -- why in the above explanaton are we missing 0 and just consider integers above 0 ... I understand the stmt B is true for SUB when we disregard 0 ---- but as u said its for all integers -- and if u consider 0 - then ADD, MUL supports STMT 2 --
Let me give you couple of examples

1. Subtraction
when n =0, n ∆ n = 0
when n = 1, n ∆ n = 0
when n = -3, n ∆ n = 0

For all integers, n ∆ n = 0

2. multiplication
when n = 0, n ∆ n = 0
when n= 1, n ∆ n = 1
when n= -2, n ∆ n = 4

we can clearly see that n ∆ n is only true when n = 0

3. division

when n = 0, n ∆ n = 0
when n= 1, n ∆ n = 1
when n= -2, n ∆ n = 1

true only when n = 0

4. addition

when n = 0, n ∆ n = 0
when n= 1, n ∆ n = 2
when n= -2, n ∆ n = -4

again true only when n = 0.
Thanks !