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by ritula » Sun Sep 14, 2008 11:15 pm
If ° represents one of the operations +, -, and x, is k °(l + m) = (k ° 1) + (k ° m) for all numbers k, l, and m?

(A) k ° 1 is not equal to 1 ° k for some numbers k.

(B) ° represents subtraction.

Ans: D
Philosophers have interpreted world in various ways, the point is to change it!
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Source: — Data Sufficiency |
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by alescau » Sun Sep 14, 2008 11:55 pm
(2) Simply replace ° with -.
(1) Notice that the condition is not satisfied by + and by x, therefore it must be - as in case (1).

k - l - m = 2k - l - m

now this would be true for k = 0, but the question says that it must hold for all k, thus we can say with certainty NO. Ans. D
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by ritula » Mon Sep 15, 2008 12:29 am
But in each case, we are getting different answers like No for (1) and Yes for (2)?
alescau wrote:(2) Simply replace ° with -.
(1) Notice that the condition is not satisfied by + and by x, therefore it must be - as in case (1).

k - l - m = 2k - l - m

now this would be true for k = 0, but the question says that it must hold for all k, thus we can say with certainty NO. Ans. D
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by alescau » Mon Sep 15, 2008 1:41 am
yes, NO for both
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