gmat prep - absolute x

[gkammaje]

OA - C

[radhaswami]

There are two cases in the main question stem

CASE 1
when x>0 implies is x=y-z?

CASE 2
When x<0 implies -x=y-z or is x+y=z

Now look at the two helps given (1) says x+y=z but it is not given if x<0 or not so INSUFFICIENT

(2) given x<o nothing about y and z so INSUFFICIENT

BOTH SUFFICIENT AS THEY SATISFY CASE2

[sanju09]

IMO B

(1) x + y = z makes x = z - y, hence mod (x) = mod (z - y), which could be equal to y - z regardless what sign is x with, only if y > z. This is because an absolute value is non-negative; and since we know nothing about y and z, hence insufficient.

(2) reads x < 0, this means that z - y < 0; and this makes us believe that 'yes', mod (x) = y - z. So (2) alone is sufficient, hence B.

[x2suresh]

IMO B

(1) x + y = z makes x = z - y, hence mod (x) = mod (z - y), which could be equal to y - z regardless what sign is x with, only if y > z. This is because an absolute value is non-negative; and since we know nothing about y and z, hence insufficient.

(2) reads x < 0, this means that z - y < 0; and this makes us believe that 'yes', mod (x) = y - z. So (2) alone is sufficient, hence B.

State 2 not given any info regarding y and z
not sufficient

It should be C.

[sanju09]

IMO C

(1) x + y = z makes x = z - y, hence mod (x) = mod (z - y), which could be equal to y - z regardless what sign is x with, only if y > z. This is because an absolute value is non-negative; and since we know nothing about y and z, hence insufficient.

(2) reads x < 0, insufficient for the same reasons as given in (1).

(1) & (2) means that z - y < 0; and this makes us believe that 'yes', mod (x) = y - z, hence C.