DelSingh
If 0<x<y, is y-x < 0.00005
(1) x>1/60,000
(2) y<1/15,000
Source: GMAT Prep question pack 1
There are two ways to deal with it.
Method 1:
Is y-x < 0.00005?
We can see that both statements alone are not sufficient.
(1) x>1/60,000
(2) y<1/15,000
We know that we can add inequalities when they have the same sign ie.
a < b
c < d
then, a+c < b+d
Also, when we multiply an inequality by -1, the inequality sign flips.
x>1/60,000 implies -x < -1/60,000
You can add these two inequalities: -x < -1/60,000 and y<1/15,000 to get y-x < 1/15000 - 1/60,000
which is y-x < 1/20,000 i.e. y-x < 0.00005
Another method is to see this on the number line. Draw a number line to understand this.
0<x<y implies that x and y are both positive and x is to the left of y on the number line.
Is y-x < 0.00005 means is the distance between x and y less than .00005?
(1) x>1/60,000
means x lies to the right of 1/60,000
(2) y<1/15,000
means y lies to the left of
4/60,000So the distance between them must be less than 4/60,000 - 1/60,000 = 3/60,000 = .00005
(see highlighted) can you explain highlighted / i mean why you write "y lies to the left of
x is greater than 1/60,000 so x can have many options same logic applies to Y if y<1/15,000 then can take numerous values
my question is why did you take these values to determine answer ---> 4/60,000 - 1/60,000 = 3/60,000