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
